Method of making a golf ball with a multi-layer core

ABSTRACT

A method for making a multilayer golf ball including a solid center having a center hardness, a plurality of laminates cut into a plurality of shapes formed around the center to create an inner ball, and a cover formed around the inner ball, wherein the plurality of layers can include at least a first layer having a hardness greater than the center hardness and a second layer having a hardness greater than the first layer hardness, and optionally a third layer disposed between the first and the second layers having a hardness greater than the first layer hardness.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.10/418,085 filed Apr. 18, 2003 now U.S. Pat. No. 7,153,467, which is acontinuation-in-part of U.S. patent application Ser. No. 09/948,692,filed Sep. 10, 2001, now U.S. Pat. No. 7,014,573, which is acontinuation-in-part of U.S. patent application Ser. No. 09/172,608,filed Oct. 15, 1998, now U.S. Pat. No. 6,302,808, which is a divisionalof U.S. patent application Ser. No. 08/943,932, filed Oct. 3, 1997, nowU.S. Pat. No. 6,056,842, and also a continuation-in-part of U.S. patentapplication Ser. No. 09/630,387, filed Aug. 1, 2000 now U.S. Pat. No.6,458,892, which is a continuation-in-part of U.S. patent applicationSer. No. 08/603,057, filed Feb. 16, 1996, now U.S. Pat. No. 5,759,676,and a continuation-in-part of U.S. patent application Ser. No.08/996,718, filed Dec. 23, 1997, now U.S. Pat. No. 6,124,389, which is acontinuation-in-part of U.S. patent application Ser. No. 08/746,362,filed Nov. 8, 1996, now U.S. Pat. No. 5,810,678, which is acontinuation-in-part of U.S. patent application Ser. No. 08/706,008,filed Aug. 30, 1996, now U.S. Pat. No. 5,813,923, which is acontinuation-in-part of U.S. patent application Ser. No. 08/603,057,filed Feb. 16, 1996, now U.S. Pat. No. 5,759,676, which is acontinuation-in-part of U.S. patent application Ser. No. 08/482,522,filed Jun. 7, 1995, now U.S. Pat. No. 5,688,191, the disclosures ofwhich are hereby incorporated by reference in their entirety.

FIELD OF THE INVENTION

The present invention is directed to a method for making a multilayergolf ball having a plurality of laminates formed around the ball. Theplurality of laminates may be formed into shells by a thermoformingprocess. The shells are then joined to form laminate layers around thegolf ball.

The plurality of laminate layers may have varying properties that may bearranged to produce a desired ball performance. The plurality oflaminate layers may include, for instance, at least a first laminatelayer having a hardness greater than the hardness of the golf ballcenter and a second laminate layer having a hardness greater than thefirst laminate layer hardness. An additional laminate layer also may bedisposed between the first and second intermediate layers having ahardness greater than the first laminate layer. The laminate layers maybe thermoplastic or thermoset materials.

BACKGROUND OF THE INVENTION

Golf ball manufacturers constantly strive to construct golf balls with abalance of good “feel,” distance, and durability. Adjusting theconstruction of the ball (e.g., providing multiple layers of materialhaving differing material properties) and/or the composition of theindividual layers (e.g., using materials having a desired high flexuralmodulus, COR, or hardness) allows golf ball manufacturers to tweak ballproperties to obtain the desired balance of golf ball properties.

Golf balls today can be of varied construction, e.g., two piece balls,three piece balls, the latter including wound balls. The difference inplay characteristics resulting from these different types ofconstructions can be quite significant.

Generally, golf balls have been classified as solid or wound balls.Solid balls having a two piece construction, typically a crosslinkedrubber core, e.g., polybutadiene crosslinked with zinc diacrylate and/orsimilar crosslinking agents, encased by a blended cover, e.g., ionomerresins, are generally most popular with the average recreational golfer.The combination of the core and cover materials provide a “hard” ballthat is virtually indestructible by golfers and one that imparts a highinitial velocity to the ball, resulting in improved distance. Becausethe materials of which the ball is formed are very rigid, two pieceballs have a hard “feel” when struck with a club. Likewise, due to theirhardness, these balls have a relatively low spin rate which providesgreater distance.

Wound balls are generally constructed from a liquid or solid centersurrounded by tensioned elastomeric material and covered with a durablecover material, e.g., ionomer resin, or a softer cover material, e.g.,balata or polyurethane. Wound balls are generally thought of asperformance golf balls and have good resiliency, desirable spincharacteristics, and feel when struck by a golf club. However, woundballs are generally difficult to manufacture when compared to solid golfballs.

The prior art includes a variety of golf balls that have been designedto provide particular playing characteristics. These characteristics aregenerally the initial velocity and spin of the golf ball, which can beoptimized for various types of players. For instance, certain playersprefer a ball that has a high spin rate in order to control and stop thegolf ball. Other players prefer a ball that has a low spin rate and highresiliency to maximize distance. Generally, a golf ball having a hardcore and a soft cover will have a high spin rate. Conversely, a golfball having a hard cover and a soft core will have a low spin rate. Golfballs having a hard core and a hard cover generally have very highresiliency for distance, but are hard feeling and difficult to controlaround the greens. A number of patents, for example, have been issuedwhich are directed towards directed towards improving the carry distanceof conventional two piece balls by altering the typical single layercore and single cover layer construction to provide a multi-layer ball,e.g., a dual cover layer, dual core layer, and/or a ball having anintermediate layer disposed between the cover and the core. U.S. Pat.Nos. 4,863,167, 5,184,828, and 4,714,253 are examples of such multilayergolf balls.

In addition, there are a number of patents directed to improving thespin, click and feel of solid balls while maintaining the distanceprovided by the solid construction golf balls. U.S. Pat. Nos. 5,072,944,4,625,964, 4,650,193, and 4,848,770 disclose a golf ball having a rubbercore and intermediate layer, e.g., polybutadiene, surrounded by a cover.U.S. Pat. Nos. 5,253,871, 5,681,898, 5,439,227, 5,556,098 are directedto golf balls having intermediate layers using a variety of materialsother than polybutadiene.

Further, there are also several patents directed to golf balls havingmultiple cover layers. U.S. Pat. Nos. 4,431,193, 5,314,187, and4,919,434 are examples of such patents. Additional examples of golfballs with multiple layers include U.S. Publication No. 2002/0028885 A1and U.S. Pat. Nos. 6,319,153 and 6,299,550.

Moreover, while the benefits of laminate layers may be generallyrecognized, manufacturing laminate layers on a golf ball presentsseveral challenges that have largely precluded their use. For example,as the desired thickness of the laminate layers becomes thinner, it isincreasingly more difficult to maintain a relatively uniform layerthickness and concentric orientation around the ball using conventionalmanufacturing methods known in the golf industry.

Retractable pin injection molding, for example, uses pins that pressagainst the core to hold it in place in the mold while layer material isbeing injected around it. The forces applied to the core to hold it inplace may cause the core surface to deform slightly. The portion of thecore near the pins may deform inwards, while other portions of the coremay deform outward. Thus, when being secured in place by retractablepins, portions of the surface of the core are slightly closer to themold walls than other portions. When the injected material is intendedto form a thin layer, these slight differences can present significantpercentage deviations in thickness. Compression molding, whichphysically compresses both the layer material and the core in order toform the layer, presents similar manufacturing difficulties as thedesired layer thickness becomes thin.

Recent developments in casting layers of the golf ball have allowed forthe manufacture of thin multilayer covers. But the casting processusually requires additional manufacturing time in order to allow thecast material to sufficiently harden or cure before opening the mold.Moreover, the use of casting only allows for one layer to be formed onthe golf ball at a time. Thus, the manufacture of a golf ball having aplurality of laminate layers would require even more time. In addition,casting also involves close control over the selection and combinationof a suitable curing agent with a pre-polymer.

Thus, it would be advantageous to provide a method of manufacturing golfballs with laminate layers without significantly increasingmanufacturing costs or manufacturing time.

SUMMARY OF THE INVENTION

The present invention is directed to the use of thermoforming processesto make an improved golf ball having a plurality of laminate layers. Theinvention includes a golf ball having a plurality of laminate layersthat form at least a portion of the golf ball. The laminate layers mayform, for example, all or part of the core, intermediate layers, orcover layers of the ball.

One embodiment of the present invention is directed to a method ofmaking a golf ball by thermoforming a plurality of shells, positioningthem around a core, and forming a cover. The plurality of shells may beformed from laminated roll stock material. In one embodiment, the rollstock may have first and second lamination layers that differ inhardness by about 10 shore D or more. In another embodiment, thedifference in hardness between the first and second lamination layersmay be even greater, such as about 15 shore D or more, or even about 20shore D or more.

In yet another embodiment, the step of thermoforming a plurality ofshells involves forming a sheet of shells from a roll stock. The shellsformed in the sheet of roll stock material may then be cut out of thesheet individually, in pairs or multiple pairs, in strips of shells, andthe like. A lip or ring may be formed around the edge of the shells whenthey are cut out of the thermoformed sheet of roll stock. In oneembodiment, the lip extends in a radial direction from the edge of theshell from about 0.01 inches to about 0.25 inches. The lip or ring maybe any shape, but in one embodiment the shape is approximately circular.Once formed, the shells may then be joined around a core. In oneembodiment, the first and second shells have similar construction anddimensions. Once in position, the shells may be compression molded aboutthe core.

The lamination layers may be any desired thickness. In one embodiment,each lamination layer has a thickness of about 0.1 inches or less. Inanother embodiment, each lamination layer has a thickness of about 0.05inches or less. It is not required that the lamination layers have thesame thickness. In one embodiment, the outermost lamination layer isabout 0.1 inches or less, while in another embodiment it is about 0.05inches or less.

The materials used for the thermoformed laminate layers need not be thesame as other layers. In one embodiment, at least one lamination layercomprises a thermoset material. For example, the thermoset material maybe polybutadiene. In another embodiment, at least one lamination layercomprises a thermoplastic material. The thermoplastic material may havea flexural modulus of about 10,000 psi or less. Additionally, thethermoplastic material may be made of ionomer resin, dynamicallyvulcanized thermoplastic elastomers, functionalized styrene-butadieneelastomers, thermoplastic rubbers, thermoplastic urethanes, metallocenepolymers, ionomer resins, or blends thereof. Other materials havingdifferent characteristics, compositions, and properties may be used aswell.

The cover may be formed by injection molding, compression molding,casting, or thermoforming process, although any additional moldingprocesses may be used as well. The cover may comprise one or more layersof material. If desired, the outermost cover may have a thickness ofabout 0.05 inches or less. Additionally, the golf ball may have a PGAcompression of about 85 or less. In another embodiment, the golf ballhas a PGA compression of about 100 or less.

In one embodiment, the shell has at least a first and second laminationlayer, with the first lamination layer being closer to the core than thesecond layer. In one embodiment, the hardness of the core, first layer,and second layer may be progressively harder from the core to the secondlamination layer. In another embodiment, the hardness of the core, firstlayer, and second layer becomes progressively softer. In one embodiment,the differences between the hardness of the core and first laminationlayer, and between the first and second lamination layers is about 5shore D or more. In another embodiment, the difference is about 10 shoreD or more.

Additional lamination layers may be thermoformed as well. For instance,one embodiment comprises a third laminate layer disposed between thefirst and second lamination layers. As mentioned above, the changes inhardness from core to the second lamination layer may be progressivelyharder or softer, although other combinations of hardness may be used aswell.

The present invention is likewise directed to golf balls having at leastone thermoformed layer. The thermoformed layer may form part or all of acover, intermediate layer, core, or combination thereof. As describedherein, the golf ball may have multiple laminate layers made of avariety of materials.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view of a golf ball formed according to thepresent invention;

FIG. 2 is a perspective view of a laminate including three layers ofcore material;

FIG. 3 is a sectional view of rollers and material being formed into thelaminate of core material;

FIG. 4 is a sectional view of a mold for forming multiple layers about acore center according to the present invention;

FIG. 5 is a sectional view of a mold forming multiple layers about acore center according to the invention with the mold-forming sheetsbeing vacuum formed within the mold;

FIG. 6 is a sectional view of a mold forming multiple layers about acore center according to the invention with the mold-forming sheetsbeing vacuum formed within the mold;

FIG. 7 is a perspective view of a half mold for use in forming multiplelayers about core centers according to the present invention;

FIG. 8 is a cross-sectional view of a compression mold of a golf ballcore according to the present invention;

FIG. 9 is an exploded view of a golf ball core according to the presentinvention in a retractable-pin injection mold;

FIG. 10 is a cross-sectional view of a golf ball core according to thepresent invention in a retractable-pin injection mold;

FIG. 11 is a cross-sectional view of a golf ball according to thepresent invention in a retractable-pin mold;

FIG. 12 is an exploded view of a golf ball core according to the presentinvention with cover layer hemispheres in a compression mold.

FIG. 13 is a perspective view of a molding apparatus for thermoforminglaminate layers of a golf ball;

FIGS. 14A-F are illustrations of a thermoforming process for use informing laminate golf ball layers;

FIGS. 15A-D are illustrations of a plug-assisted thermoforming processfor use in forming laminate golf ball layers;

FIG. 16 is a perspective view of two thermoformed shells that join toform a plurality of laminate layers around a golf ball;

FIG. 17 is a perspective view of a web assembly of thermoformed shells.

DETAILED DESCRIPTION OF THE INVENTION

The present invention is directed to golf balls having a plurality oflaminate layers formed by thermoforming sheets of material into shells.The shells are then joined together to form the laminate layers of theball. The plurality of laminate layers may form any portion of the golfball, including the core, an intermediate layer, or the cover.

One advantage of the present invention is that it allows for themanufacture of golf balls having thin layers of material of a relativelyuniform thickness. The present invention also allows laminate layers tobe more easily formed concentric with the center of the ball. The resultis greater flexibility in the design of golf balls in order to obtainexcellent playing characteristics, such as resiliency, spin rate, andfeel. Moreover, the present invention also simplifies the manufacturingprocess for making such laminate layers and thereby reducesmanufacturing costs.

In particular, the present invention uses raw material in roll stockform to form the shells of the ball by a thermoforming process.Thermoforming processes are high volume methods of producing moldedproducts from a thin sheet of roll stock. While this molding process isprincipally used with thermoplastic materials, it is also possible touse thermoset materials as well.

Thermoforming processes generally involve heating a sheet of materialuntil the sheet softens and then forcing the sheet against a coolforming mold by vacuum or pressure. Positive or negative pressure isthen employed to push, pull, or stretch the softened sheet into a cavityor onto a protrusion corresponding to the shape of the desired part. Thesheet is held in place against the mold surface while it cools. Once ithas sufficiently cooled, the sheet retains the shape of the mold evenafter being removed from the cavity or protrusion. There are severalvariations of thermoforming, such as vacuum, positive air pressure, plugassist, draping, twin sheet, positive, negative, vacuum snap-back, andbillow forming. Some of these techniques are explained in greater detailbelow to illustrate the invention, although a skilled artisan wouldunderstand that a wide variety of additional thermoforming techniquescould be used without departing from the spirit and scope of theinvention.

The sheet of material used in a thermoforming process may be provided inroll stock. Generally, roll stock is a sheet of material that is rolledalong its length to form a cylindrical shape. Typically, the roll stockis about 420 mm to about 660 mm wide, and has a thickness correspondingapproximately to the desired thickness of the finished product or layer.As explained more fully below, the roll stock is connected to athermoforming machine and delivered to the forming module.

FIG. 13 illustrates one embodiment of a thermoforming mold that may beused with the present invention. As shown, the thermoforming machine orprocess can carry out several stages of the molding processsimultaneously. For instance, a portion of the roll stock may be beingpre-heated while other portions of the roll stock are being molded,undergoing further processing or finishing, or are being off-loaded forfurther processing at another location.

Roll stock is connected to the thermoforming machine at a loadingstation. In this embodiment, roll stock is rolled or wrapped around acylindrical tube that may be placed on a roller so that it can rotate aslayer material is supplied to the forming module. As the material isunwound, it is preheated and then molded into its desired shape.

In one embodiment of the present invention, the material is formed intoa plurality of shells. The desired number of shells molded in a singlemolding cycle may vary according to the size of the roll stock, althoughother factors also may determine what number of shells are formed ineach molding cycle as well. As the width of the roll stock increases,the number of shells that may be formed in a single mold cycleincreases. For instance, if the roll stock is about 660 mm wide, thenumber of shells that may be formed in a single molding cycle may beabout 65 shells or more, more preferably about 85 shells or more, andeven more preferably about 100 shells or more. In contrast, if a rollstock is about 420 mm wide, the number of shells that may be formed in asingle molding cycle may be about 40 or more, more preferably about 50or more, and even more preferably about 60 or more.

The duration of a mold cycle may be determined by the length of time ittakes from loading roll stock material into the mold to removing it fromthe mold. Preferably, a single mold cycle is relatively short induration. For example, a single mold cycle may last approximately 30seconds or less, but more preferably lasts less than about 10 seconds.More preferably, the cycle rate is approximately 10 cycles per minute.In this preferred embodiment, a thermoforming mold having 100 cavitiesand running at 10 cycles per minute can make approximately 1000 coversper minute.

The thermoforming mold in one embodiment of the present invention has aroll stock supply mechanism that controls the rate at which the sheet ofmaterial is fed into the molding machine. One example of a suitablestock supply mechanism is a servo driven chain drive, although oneskilled in the art would understand that any method or structure may beused to help move the roll stock through the molding process. In use,the supply mechanism delivers the sheet of roll stock to a pre-heatingstation—where the material is heated until soft. Once the material hasbeen sufficiently softened, the supply mechanism delivers the sheet ofroll stock to the mold cavities so that the material can be formed intothe desired shape. Once formed, the material is then delivered to anyadditional processing station or offloaded from the thermoformingmachine.

FIGS. 14A-F illustrate an example of a thermoforming process in greaterdetail. In general the thermoforming process may be divided into 6steps. First, as shown in FIG. 14A, the roll stock is delivered to apreheating station where it is softened prior to being molded. In thisembodiment, the forming station is opened so that the roll stock may befed into the preheating station. Preferably, the roll stock is heldbetween the upper portion of the preheater and the heating elementsuntil the material is fully positioned within the preheater.

Next, with the reference to FIG. 14B, once the roll stock is positionedwithin the preheater, the preheater is closed so that the lower surfaceof the roll stock is drawn near to or against the heating plate. Whilethe figures illustrate the lower portion or the mold moving upwards ordownwards in order to close or open the mold, this illustration does notlimit the manner in which the portions of the mold move with respect toeach other. In one embodiment, a vacuum can be applied to further assistin drawing the roll stock to the heating plate. The heating elements ofthe thermoforming mold may use any suitable structure or method tosoften the roll stock. Examples of such suitable structures or methodsmay include, without limitation, radiant heat or ultrasonic vibration.Yet another example of a suitable structure or method to soften the rollstock would include steam heating or by electrically heating the rollstock. Two examples of infrared heaters that may be used to soften theroll stock are ceramic heaters and quartz tube heaters.

It is preferred that the roll stock be sufficiently softened so thatthey can deform easily. Over time, such as by repeated molding cycles,the mold plates can rise in temperature due to the dissipation of heatfrom the molded material. If the mold plates become too hot, however,the material may not cool sufficiently to allow it to set in its desiredshape. To address the build-up of heat, the walls of the mold cavity maybe chilled so that as the material is quenced or cooled as it comes intocontact with the cavity wall. The cooling of the mold may beaccomplished by any suitable means known to those skilled in the art.For instance, the mold may be chilled with water or glyol. Air coolingthe mold cavity may also help maintain the mold below the distortion orset temperature of the sheet of material.

Turning now to FIG. 14C, once the roll stock has been adequatelysoftened, the preheater may be aerated to equalize the pressure betweenthe inside of the preheater and the outside. This step is particularlyhelpful when a vacuum is used to draw the roll stock to the heatingplate as described above. Once the pressure has become relativelyequalized, the mold is opened so that the roll stock may be transportedto and positioned over the mold cavities as shown in FIG. 14D. As shownin FIG. 14D, the delivery of the softened roll stock to the moldcavities in turn may cause additional material to be supplied to thepreheater. In this embodiment, it is preferably that the time needed forsoftening the material and the time needed to form and cool the sheetagainst the mold surface are controlled so that both processes arecompleted at about the same time.

Once the softened roll stock is properly positioned over the cavities,the mold is closed and a vacuum is applied to one side of the mold todraw the softened material toward or against the mold wall. This step isshown in FIG. 14E. Additionally, compressed air may be forced into themold on the opposite side of the material where the vacuum is applied inorder to further ensure that the material is pressed against the moldwall. The material is then cooled as it is pressed against the moldwall. Eventually, the material is sufficiently cooled that is willretain its molded shape.

Once cooled, the pressure in the mold is again equalized so that themold can be opened and the molded material removed (FIG. 14F). Toaccomplish this, air may be vented into the portion of the mold wherethe vacuum was applied. Air also may be vented or vacuumed out of theportion of the mold where compressed gases were forced inside. As themolded material is removed, any additional portion of the roll stockbeing preheated may then be delivered to the mold.

One skilled in the art would appreciate that several variations of themolding process described above are possible without departing from thespirit and scope of the present invention. FIGS. 15A-D, for example,provides one alternative molding process that also falls within thescope of the present invention. These figures illustrate that a plug orother suitable device may be used to assist in drawing the softened rollstock against the mold. For instance, FIG. 15A illustrates that once theroll stock is sufficiently soft, it is positioned within the mold sothat the plug resides above the material. As illustrated in FIG. 15B,the use of a plug or similar structure preferably is combined with thevacuum forming process described above. The mold is then closed, avacuum is applied and the plug is lowered to press the material againstthe mold wall. Compressed gasses also may be delivered into the upperportion of the mold, as shown in FIG. 15C.

Application of the vacuum, plug, and compressed air may be staged sothat the rate or degree that material is drawn to or held against themold can vary during the mold cycle. For example, the time at which theplug and compressed air are applied can be staged or delayed until thevacuum has first drawn the material toward the mold wall. The plug and,optionally, compressed air may then be applied to press the roll stockagainst the mold wall. Likewise, application of the plug and/orcompressed air against the roll stock may discontinue prior tocompletion of the mold cycle. Alternatively, the plug may be used toprestretch the sheet prior to applying a vacuum or compressed air. Oncethe molding cycle is nearly complete, the pressure in the mold isequalized so that the mold can be opened and the molded materialremoved.

In yet another alternative embodiment of the present invention, apositive forming process also may be used to thermoform a layer of agolf ball. For example, the softened sheet of material may be positionedover a male or positive mold. The sheet then may be draped over thepositive mold until the sheet forms a seal around the outer edge of themold. Trapped air may then be evacuated by vacuum holes along theprotrusion of the male mold. Alternatively, or in addition to applying avacuum, forced air or other gases may be applied to the opposite side ofthe sheet that contacts the mold, thereby blowing the sheet intoposition. The vacuum and/or applied pressure causes the sheet to bepressed against the mold surface while it cools.

Twin sheet thermoforming processes also may be used to form a golf balllayer. This process is similar to the vacuum process described above,but forms two sheets into opposing mold halves at the same time. Themolded sheets may then be fused or connected together while the sheetsare still in a softened state. Preferably, however, a golf ball core isplaced inside the formed sheets prior to them being connected together.

In all of these examples, the formed material is removed from the moldonce the sheet has sufficiently cooled to retain the molded shape.Removal of the molded sheet may be assisted by applying pressurizedgases between the mold wall and the sheet of material. For instance,forced air may be directed through openings or vents on the mold surfacethat previously were used to form a vacuum. The use of pressurizedgasses to remove the formed sheet may be particularly beneficial inpositive forming, although it may be useful in other thermoformingprocesses as well.

As described above, the material may be molded into shells that may bejoined to form the laminate layers of the golf ball. FIG. 16 illustratesone example of an assembly of two shells applied over a component partof a golf ball, such as a core. The shells are generally hemisphericalin shape with inner diameters corresponding approximately to the outerdiameter of the ball placed inside. In this embodiment, the shells usedin the assembly have a molded lip that extends outward from theperimeter of the base of the shell.

Preferably, a plurality of shells are thermoformed during each moldingcycle. Once molded, the sheet of molded shells can be prepared forfurther processing. In the embodiment shown in FIG. 16, individualshells are cut from the molded sheet such that the shells have lips orrings. Preferably, the end of the shell corresponding approximately tothe equator of the ball has a ring or lip that extends outward inapproximately a radial direction so that when two shells are joinedaround a core or other golf ball component the surfaces of the moldedlips are approximately parallel.

Alternatively, as the molded roll stock is removed from the mold cavity,the shells may remain in the sheet as it is removed from the machine.Two sheets of molded roll stock may then be used to mold the shellsaround a plurality of centers placed within the shells. In anotherembodiment, the shells formed in the molded roll stock may be punchedout, cut, or otherwise separated from each other. For instance, theshells may be punched out from the sheet of molded roll stock and thenassembled around cores individually.

In yet another alternative embodiment, the shells may be cut from theroll stock in pairs, or multiple pairs, so that the cores may be placedin a shell or plurality of shells on one side of the cut sheet. Thesheet may then be folded so that a second shell is placed over the core.The surfaces of the sheet that contact each other once the sheet isfolded may be tack welded or otherwise joined so that the assembly ofcores and shells remains in a desired position for further processing.Alternatively, a crease may be formed where the sheet is folded to helpmaintain the positioning of the shells and cores. The crease may beformed by applying pressure, heat, or both along the folded edge of thesheet.

It is not necessary in every instance that the shells cut from the rollstock should be in pairs or multiple pairs. For example, the sheet maybe cut so that a plurality of shells remain attached or connected toeach other. The sheet may be cut in strips, for instance, thatcorrespond to the cavity configuration of at least a portion of acompression mold. Cores may be placed within the strip of shells. Oncethe cores are in position, a second set of shells may then be placedover them. The second set of shells may be a similarly configured stripcut from a larger sheet of thermoformed shells, may be individualshells, or may have a different configuration.

Returning to the embodiment shown in FIG. 16, the width of the lip fromthe outer surface of the shell to the outermost edge of the ring may beany length, such as between about 0.05 inches to about 0.5 inches orbetween about 0.063 inches and 0.3 inches. Depending upon the subsequentprocessing steps that will be taken to complete the manufacture of thegolf ball, the width of the lip may have a beneficial minimum length ormaximum length. For instance, the minimum width of the lip may be atleast about 0.63 inches, at least about 0.093 inches, at least about0.125 inches, or at least about 2 inches. Likewise, the maximum width ofthe lip may be about 0.3 inches or less, about 0.188 inches or less, orabout 0.125 inches or less. These upper and lower limits also may becombined in any manner. For example, the width of the lip may be betweenabout 0.063 inches and about 0.188 inches, or may be between about 0.093inches or about 0.125 inches.

When two shells are joined, the surfaces of the rings or lips may betacked together to hold the assembly together until it is ready foradditional processing. Additionally, the rings may assist in properlypositioning or aligning the shells in a mold in subsequent moldingprocesses for the ball, such as compression molding or other processesdescribed herein.

Yet another benefit of using molded lips or rings is that the innersurface of the shells may be molded to closely correspond to the outersurface of the component placed inside the shells. For instance, a corecan be placed inside shells with inner surfaces having a curvatureclosely corresponding to the core's outer diameter. One benefit of thisconfiguration is that it may reduce or eliminate the occurrence oftrapped air or gases between the shells and the core during subsequentmolding. For example, the molded lips may be tacked together to hold theassembly together prior to compression molding the shells around thecore. Alternatively, the shells may be configured and adapted such thatfrictional forces hold the shell on the core.

The shells and ball may be placed in a compression mold to fuse the twoshells together around the ball. Preferably the compression moldprimarily applies pressure and heat where the two shells meet, and doesnot apply uneven pressure to other portions of the ball.

FIG. 17 illustrates another embodiment of the invention in which a sheetof molded shells are prepared for further processing without firstcutting individual shells as described above and illustrated in FIG. 16.Instead, the shells remain in the thermoformed sheet. Cores are thenplaced inside the shells and a second sheet of thermoformed material maythen be placed over the cores. The assembly of the sheets and cores maybe tack welded or held together in any suitable manner, examples ofwhich are already described herein.

The roll stock may be made of any material or combination of materialsaccording to the number and features of the laminate layers desired tobe formed on the golf ball. Many examples of the types of materials thatmay be used are provided in greater detail below. Preferably, the rollstock is preformed with a plurality of layers, each layer correspondingto a laminate layer of the ball. Thus, the roll stock may be made ofco-extruded films of material. The material properties of each film neednot be identical, or even similar, to the neighboring laminate layer.For instance, one laminate layer may be thermoplastic, while another isthermoset. Additionally, the hardness of one layer may be greater thanthe hardness of another. For instance, the hardness of one layer mayhave a hardness that is about 10 shore D or greater than a neighboringlayer. Additionally, in one embodiment the difference in hardnessbetween the laminate layers may be from about 3 to about 20 shore D, butmore preferably may be from about 5 to about 15 shore D.

In another embodiment, the laminate layers may differ in hardness by alesser degree. For example, the layers may differ in hardness by fromabout 5 to 40 shore C, but also may differ in hardness by about 20 shoreC or less. More preferably, the laminate layers may differ in hardnessby about 10 shore C.

The thermoformed laminate layer may be used to form any portion of thegolf ball in whole or in part, including the core, an intermediatelayer, or a cover. The following examples of various embodiments of theinvention further illustrate the types of golf balls and laminate layersthat may be made under the present invention. A skilled artisan wouldappreciate, however, that the following discussion illustrates theinvention without limiting it to only the embodiments discussed.

FIG. 1 shows a multilayer golf ball according to one embodiment of thepresent invention. Golf ball 10 includes a center 11, a first layer 12,a second layer 13, a third layer 14, and a cover 15. The first, second,and third layers may be of the same or different material. As usedherein, the term “core layer” means any layer surrounding the center ofthe ball, but not the outermost layer, and, therefore, the term may beused interchangeably with the term “intermediate layer.”

As used herein, the term “layer” includes any generally sphericalportion of a golf ball or golf ball core, center, intermediate, orcover, including a one-piece ball. An “intermediate layer” is definedherein as a portion of the golf ball that occupies a volume between thecover and the core. Of course, as one of ordinary skill in the art wouldrecognize, any of the core, cover, and intermediate of the golf balls ofthe invention can be formed of one layer or a plurality of layers, asthat term is defined herein.

As used herein, the term “multilayer” means at least two layers andincludes fluid-center balls, hollow-center balls, and balls with atleast two intermediate layers and/or cover layers.

The following terms that are used in this application are defined interms of the enumerated ASTM tests:

Specific gravity ASTM D - 297 Flexural (Flex) Modulus ASTM D - 6272-98,Procedure B Shore C & D Hardness ASTM D - 2240-00 Melt flow index ASTMTest D 1238, Condition E, Procedure AThe Center

The golf balls of the present invention are formed with a center havinga low compression, but still exhibit a finished ball COR and initialvelocity approaching that of conventional two-piece distance balls.Preferably, the center employed in the golf balls of the presentinvention have a compression of about 60 or less, more preferably about45 to about 60 and most preferably about 50 to about 55. As used herein,the term “about,” used in connection with one or more numbers ornumerical ranges, should be understood to refer to all such numbers,including all numbers in a range. Likewise, it is preferred that thefinished balls made with such centers have a COR, measured at an inboundspeed of 125 ft./s., of about 0.795 to about 0.815, more preferablyabout 0.797 to about 0.812 and most preferably about 0.800 to about0.810.

As used herein, “COR” refers to Coefficient of Restitution, which isobtained by dividing a ball's rebound velocity by its initial (i.e.,incoming) velocity. This test is performed by firing the samples out ofan air cannon at a vertical steel plate over a range of test velocities(from 75 to 150 ft/s). A golf ball having a high COR dissipates asmaller fraction of its total energy when colliding with the plate andrebounding therefrom than does a ball with a lower COR. Unless otherwisenoted, the COR values reported herein are the values determined at anincoming velocity of 125 ft/s.

In a preferred embodiment, the center has a Shore C hardness of about 65to about 80, more preferably about 68 to about 75 and most preferablyabout 72 to about 75.

The centers employed in the golf balls of the present inventionpreferably have a diameter of about 1.25 inches to about 1.51 inches,more preferably about 1.30 inches to about 1.48 inches and mostpreferably about 1.39 inches. The overall diameter of the center and theintermediate layer is about 84 percent to about 97 percent of theoverall diameter of the finished ball.

A representative base composition for forming the centers employed inthe present invention includes polybutadiene and, in parts by weightbased on 100 parts polybutadiene, 20 to 50 parts of a metal saltdiacrylate, dimethacrylate, or monomethacrylate, preferably zincdiacrylate. The polybutadiene preferably has a cis-1,4 content of aboveabout 90 percent and more preferably above about 96 percent. Commercialsources of polybutadiene include Shell 1220 manufactured by ShellChemical, NEOCIS® BR40 manufactured by Enichem Elastomers, UBEPOL® BR150manufactured by Ube Industries, Ltd, and CB23 available BayerCorporation of Akron, Ohio. If desired, the polybutadiene can also bemixed with other elastomers known in the art, such as natural rubber,styrene butadiene, and/or isoprene in order to further modify theproperties of the center. When a mixture of elastomers is used, theamounts of other constituents in the center composition are usuallybased on 100 parts by weight of the total elastomer mixture.

Metal salt diacrylates, dimethacrylates, and monomethacrylates suitablefor use in the center employed in this invention include those whereinthe metal is magnesium, calcium, zinc, aluminum, sodium, lithium ornickel. Zinc diacrylate is preferred, because it provides golf ballswith a high initial velocity in the United States Golf Association(“USGA”) test. The zinc diacrylate can be of various grades of purity.For the purposes of this invention, the lower the quantity of zincstearate present in the zinc diacrylate the higher the zinc diacrylatepurity. Zinc diacrylate containing less than about 10 percent zincstearate is preferable. More preferable is zinc diacrylate containingabout 4 to about 8 percent zinc stearate. Suitable, commerciallyavailable zinc diacrylates include those from Rockland React-Rite andSartomer. The preferred concentrations of zinc diacrylate that can beused are 20 to 50 parts per hundred (pph) based upon 100 pph ofpolybutadiene or alternately, polybutadiene with a mixture of otherelastomers that equal 100 pph. As used herein, the term “pph” inconnection with a batch formulation refers parts by weight of theconstituent per hundred parts of the base composition.

Free radical initiators are used to promote cross-linking of the metalsalt diacrylate, dimethacrylate, or monomethacrylate and thepolybutadiene. Suitable free radical initiators for use in the inventioninclude, but are not limited to peroxide compounds, such as dicumylperoxide; 1,1-di(t-butylperoxy)3,3,5-trimethyl cyclohexane; bis(t-butylperoxy) diisopropylbenzene; 2,5-dimethyl-2,5 di (t-butylperoxy)hexane; or di-t-butyl peroxide; and mixtures thereof. Other usefulinitiators would be readily apparent to one of ordinary skill in the artwithout any need for experimentation. The initiator(s) at 100 percentactivity are preferably added in an amount ranging between about 0.05and about 2.5 pph based upon 100 parts of butadiene, or butadiene mixedwith one or more other elastomers. More preferably, the amount ofinitiator added ranges between about 0.15 and about 2 pph and mostpreferably between about 0.25 and about 1.5 pph.

Typical prior art golf ball centers incorporate 5 to 50 pph of zincoxide (ZnO) in a zinc diacrylate-peroxide cure system that cross-linkspolybutadiene during the core molding process. However, in oneembodiment of the present invention the ZnO in the center compositionmay be eliminated in favor of calcium oxide (CaO). Centers produced froman admixture containing CaO may exhibit desirable performanceproperties. For instance, when replacing ZnO with CaO may allow theinitial velocity and COR of the center to be maintained while reducingthe compression of the center by at least about 4 compression points onthe standard compression scale, and may be reduced as much as 6 points.

As used herein, the terms “points” or “compression points” refer to thecompression scale or the compression scale based on the ATTI EngineeringCompression Tester. This scale, which is well known to those working inthis field, is used in determining the relative compression of a centeror ball. Some artisans use the Reihle compression scale instead of thestandard compression scale. Based on disclosure in U.S. Pat. No.5,368,304, column 20, lines 55-53 it appears that Reihle compressionvalues can be converted to compression values through the use of thefollowing equation:compression value=160−Reihle compression value.

Additionally, the combination of the use of calcium oxide and a higherpercentage of zinc diacrylate can be used to maintain the samecompression as with the zinc oxide, but the initial velocity and COR issignificantly increased. Thus, by using calcium oxide, either the centercompression can be lowered and the initial velocity and COR maintainedor the amount of zinc diacrylate can be increased so that the centercompression is the same and the initial velocity and COR is increased.

The amount of calcium oxide added to the center-forming composition maybe from about 0.1 to about 15, preferably 1 to 10, most preferably 1.25to 5, parts calcium oxide per hundred parts of polybutadiene.

In yet another, more preferred, embodiment, however, the core mayinclude halogenated organosulfur compounds, such as those described inapplication Ser. No. 09/951,963 filed on Sep. 13, 2001, the entirety ofwhich is incorporated herein by reference. The halogenated organosulfercompounds of the present invention may include, but are not limited tothose having the general formula:

where R₁-R₅ can be C₁-C₈ alkyl groups; halogen groups; thiol groups(—SH), carboxylated groups; sulfonated groups; and hydrogen; in anyorder; and also pentafluorothiophenol; 2-fluorothiophenol;3-fluorothiophenol; 4-fluorothiophenol; 2,3-fluorothiophenol;2,4-fluorothiophenol; 3,4-fluorothiophenol; 3,5-fluorothiophenol2,3,4-fluorothiophenol; 3,4,5-fluorothiophenol;2,3,4,5-tetrafluorothiophenol; 2,3,5,6-tetrafluorothiophenol;4-chlorotetrafluorothiophenol; pentachlorothiophenol;2-chlorothiophenol; 3-chlorothiophenol; 4-chlorothiophenol;2,3-chlorothiophenol; 2,4-chlorothiophenol; 3,4-chlorothiophenol;3,5-chlorothiophenol; 2,3,4-chlorothiophenol; 3,4,5-chlorothiophenol;2,3,4,5-tetrachlorothiophenol; 2,3,5,6-tetrachlorothiophenol;pentabromothiophenol; 2-bromothiophenol; 3-bromothiophenol;4-bromothiophenol; 2,3-bromothiophenol; 2,4-bromothiophenol;3,4-bromothiophenol; 3,5-bromothiophenol; 2,3,4-bromothiophenol;3,4,5-bromothiophenol; 2,3,4,5-tetrabromothiophenol;2,3,5,6-tetrabromothiophenol; pentaiodothiophenol; 2-iodothiophenol;3-iodothiophenol; 4-iodothiophenol; 2,3-iodothiophenol;2,4-iodothiophenol; 3,4-iodothiophenol; 3,5-iodothiophenol;2,3,4-iodothiophenol; 3,4,5-iodothiophenol; 2,3,4,5-tetraiodothiophenol;2,3,5,6-tetraiodothiophenoland; and their zinc salts, the metal saltsthereof, and mixtures thereof, but is preferably pentachlorothiophenolor the metal salt thereof. The metal salt may be zinc, calcium,potassium, magnesium, sodium, and lithium, but is preferably zinc.

Preferably, the halogenated organosulfur compound ispentachlorothiophenol, which is commercially available in neat form orunder the tradename STRUKTOL®, a clay-based carrier containing thesulfur compound pentachlorothiophenol loaded at 45 percent (correlatingto 2.4 parts PCTP). STRUKTOL® is commercially available from StruktolCompany of America of Stow, Ohio. PCTP is commercially available in neatform from eChinachem of San Francisco, Calif. and in the salt form fromeChinachem of San Francisco, Calif. Most preferably, the halogenatedorganosulfur compound is the zinc salt of pentachlorothiophenol, whichis commercially available from eChinachem of San Francisco, Calif. Thehalogenated organosulfur compounds of the present invention arepreferably present in an amount greater than about 2.2 pph, morepreferably between about 2.3 pph and about 5 pph, and most preferablybetween about 2.3 and about 4 pph.

The center compositions employed in the present invention may alsoinclude fillers, added to the elastomeric composition to adjust thedensity and/or specific gravity of the center. As used herein, the term“fillers” includes any compound or composition that can be used to varythe density and other properties of the subject golf ball center.Fillers useful in the golf ball center according to the presentinvention include, for example mineral fillers such as zinc oxide (in anamount significantly less than that which would be necessary without theaddition of the calcium oxide), barium sulfate, and regrind (which isrecycled core molding matrix ground to 30 mesh particle size). Otherexamples of fillers include, but are not limited to tungsten and clays.The amount and type of filler utilized is governed by the amount andweight of other ingredients in the composition, since a maximum golfball weight of 1.620 oz has been established by the USGA. Appropriatefillers generally used range in specific gravity from about 2.0 to about5.6, although the specific gravity of some fillers may be even higher.The specific gravity of a tungsten filler, for instance, may be about19. In the preferred golf ball, the amount of filler in the center islower than that of a typical golf ball such that the specific gravity ofthe center is decreased.

The preferred range of specific gravities of the centers employed in thepresent invention is from about 1.0 to about 1.2, more preferably in therange of about 1.1 to about 1.18, depending upon the size of the center,cover, intermediate layer and finished ball, as well as the specificgravity of the cover and intermediate layer.

Other ingredients such as accelerators, e.g. tetra methylthiuram,processing aids, processing oils, plasticizers, dyes and pigments,antioxidants, as well as other additives well known to the skilledartisan may also be used in the present invention in amounts sufficientto achieve the purpose for which they are typically used.

The Intermediate Layer(s)

The intermediate layer(s) may be formed from dynamically vulcanizedthermoplastic elastomers, functionalized styrene-butadiene elastomers,thermoplastic rubbers, thermoset elastomers, thermoplastic urethanes,metallocene polymers, thermoset urethanes, ionomer resins, or blendsthereof. In a preferred embodiment of the present invention, theintermediate layer includes a thermoplastic or thermoset polyurethane.

Suitable dynamically vulcanized thermoplastic elastomers includeSANTOPRENE®, SARLINK®, VYRAM®, DYTRON® and VISTAFLEX®. SANTOPRENE® isthe trademark for a dynamically vulcanized PP/EPDM. SANTOPRENE® 203-40is an example of a preferred SANTOPRENE® and is commercially availablefrom Advanced Elastomer Systems.

Examples of suitable functionalized styrene-butadiene elastomers, i.e.,styrene-butadiene elastomers with functional groups such as maleicanhydride or sulfonic acid, include KRATON FG-1901x and FG-1921x, whichare available from the Shell Corporation of Houston, Tex.

Examples of suitable thermoplastic polyurethanes include ESTANE® 58133,ESTANE® 58134 and ESTANE® 58144, which are commercially available fromthe B.F. Goodrich Company of Cleveland, Ohio.

Suitable metallocene polymers, i.e., polymers formed with a metallocenecatalyst include those commercially available from Sentinel Products ofHyannis, Mass. Suitable thermoplastic polyesters include polybutyleneterephthalate.

Suitable thermoplastic ionomer resins are obtained by providing a crossmetallic bond to polymers of monoolefin with at least one memberselected from the group consisting of unsaturated mono- or di-carboxylicacids having 3 to 12 carbon atoms and esters thereof (the polymercontains 1 to 50 percent by weight of the unsaturated mono- ordi-carboxylic acid and/or ester thereof). More particularly, low modulusionomers such as acid-containing ethylene copolymer ionomers, includeE/X/Y copolymers where E is ethylene, X is a softening comonomer such asacrylate or methacrylate present in 0-50 (preferably 0-25, mostpreferably 0-2), weight percent of the polymer, and Y is acrylic ormethacrylic acid present in 5-35 (preferably 10-35, most preferably15-35, making the ionomer a high acid ionomer) weight percent of thepolymer, wherein the acid moiety is neutralized 1-90 percent (preferablyat least 40 percent, most preferably at least about 60 percent) to forman ionomer by a cation such as lithium*, sodium*, potassium, magnesium*,calcium, barium, lead, tin, zinc* or aluminum (*=preferred), or acombination of such cations. Specific acid-containing ethylenecopolymers include ethylene/acrylic acid, ethylene/methacrylic acid,ethylene/acrylic acid/n-butyl acrylate, ethylene/methacrylicacid/n-butyl acrylate, ethylene/methacrylic acid/iso-butyl acrylate,ethylene/acrylic acid/iso-butyl acrylate, ethylene/methacrylicacid/n-butyl methacrylate, ethylene/acrylic acid/methyl methacrylate,ethylene/acrylic acid/methyl acrylate, ethylene/methacrylic acid/methylacrylate, ethylene/methacrylic acid/methyl methacrylate, andethylene/acrylic acid/n-butyl methacrylate. Preferred acid-containingethylene copolymers include ethylene/methacrylic acid, ethylene/acrylicacid, ethylene/methacrylic acid/n-butyl acrylate, ethylene/acrylicacid/n-butyl acrylate, ethylene/methacrylic acid/methyl acrylate andethylene/acrylic acid/methyl acrylate copolymers. The most preferredacid-containing ethylene copolymers are ethylene/methacrylic acid,ethylene/acrylic acid, ethylene/(meth)acrylic acid/n-butyl acrylate,ethylene/(meth)acrylic acid/ethyl acrylate, and ethylene/(meth)acrylicacid/methyl acrylate copolymers.

Such ionomer resins include SURLYN® and Iotek®, which are commerciallyavailable from DuPont and Exxon, respectively.

In another preferred embodiment of the present invention, theintermediate layer is a blend of a first and a second component whereinthe first component is a dynamically vulcanized thermoplastic elastomer,a functionalized styrene-butadiene elastomer, a thermoplastic orthermoset polyurethane or a metallocene polymer and the second componentis a material such as a thermoplastic or thermoset polyurethane, athermoplastic polyetherester or polyetheramide, a thermoplastic ionomerresin, a thermoplastic polyester, another dynamically vulcanizedelastomer, another a functionalized styrene-butadiene elastomer, anothera metallocene polymer or blends thereof. In a more preferred embodiment,at least one of the first and second components includes a thermoplasticor thermoset polyurethane.

Such thermoplastic blends useful in the intermediate layers of the golfball of the present invention preferably include about 1 percent toabout 99 percent by weight of a first thermoplastic and about 99 percentto about 1 percent by weight of a second thermoplastic. Preferably thethermoplastic blend includes about 5 percent to about 95 percent byweight of a first thermoplastic and about 5 percent to about 95 percentby weight of a second thermoplastic. In a preferred embodiment of thepresent invention, the first thermoplastic material of the blend is adynamically vulcanized thermoplastic elastomer, such as Santoprene®.

The intermediate layer of the present invention may be formed from anintermediate layer blend including up to 100 percent by weight of anethylene methacrylic/acrylic acid copolymer. As used herein, the term“copolymer” refers to a polymer which is formed from two or moremonomers. Below is a non-limiting example of the chemical structure forsuitable ethylene methacrylic/acrylic acid copolymers:

wherein x=50 to 99 percent;

-   -   y=1 to 50 percent;    -   z=0 to 49 percent;    -   R₁═H or CH₃;    -   R₂═CH₃ or isobornyl; and    -   n=0 to 12.

Specific acid-containing ethylene copolymers include ethylene/acrylicacid; ethylene/methacrylic acid; ethylene/acrylic acid/n- or isobutylacrylate; ethylene/methacrylic acid/n- or iso-butyl acrylate;ethylene/acrylic acid/methyl acrylate; ethylene/methacrylic acid/methylacrylate; ethylene/acrylic acid/iso-bornyl acrylate or methacrylate andethylene/methacrylic acid/isobornyl acrylate or methacrylate. Suitableethylene methacrylic/acrylic acid copolymers are sold commercially byDuPont under the tradename NUCREL®, with NUCREL® 960, NUCREL® RX9-1, and010 being preferred.

In one embodiment, the intermediate layer is formed from a blend whichincludes an ethylene methacrylic/acrylic acid copolymer.

In another embodiment of the present invention, the intermediate layeris formed from a blend which includes an ethylene methacrylic/acrylicacid copolymer and a second component which includes a thermoplasticmaterial. Suitable thermoplastic materials for use in the intermediateblend include, but are not limited to, polyesterester block copolymers,polyetherester block copolymers, polyetheramide block copolymers,ionomer resins, dynamically vulcanized thermoplastic elastomers,styrene-butadiene elastomers with functional groups such as maleicanhydride or sulfonic acid attached, thermoplastic polyurethanes,thermoplastic polyesters, polymers formed using a metallocene catalyst(“metallocene polymers”) and/or blends thereof.

Suitable thermoplastic polyetheresters include materials which arecommercially available from DuPont under the tradename HYTREL® andinclude HYTREL® 3078, HYTREL® G3548W, HYTREL® G4078W, and HYTREL® 4069.

Suitable thermoplastic polyetheramides are commercially available fromElf-Atochem of Philadelphia, Pa., under the tradename PEBAX® and includePEBAX® 2533, PEBAX® 1205 and PEBAX® 4033.

Preferably, the second component of the intermediate layer blendincludes polyetherester block copolymer, with HYTREL® 3078 being aparticularly preferred polyetherester block copolymer.

Other conventional materials, such as balata, elastomer and polyethylenemay also be used in the first, second and third layers 12, 13 and 14 ofthe present invention.

Many prior art intermediate layers generally have a specific gravity ofabout 1 or less. However, in a preferred embodiment, the intermediatelayer employed in the golf balls of the present invention have aspecific gravity greater than 1.2, preferably about 1.21 to about 1.30,more preferably about 1.23 to about 1.29 and most preferably about 1.27.

The desired specific gravity of the intermediate layer may be obtainedby adding a filler such as barium sulfate, zinc oxide, titanium dioxideand combinations thereof to the intermediate layer blend. Zinc oxide isthe preferred filler.

In one embodiment of the present invention, the intermediate layer isformed from a blend of about 1 to about 99 percent by weight ethylenemethacrylic/acrylic acid copolymer, about 0 to about 75 percent byweight of the second thermoplastic component (as described above) andabout 0 to about 50 percent by weight zinc oxide. In another embodimentof the present invention, the intermediate layer is formed from a blendof about 10 to 50 percent by weight ethylene methacrylic/acrylic acidcopolymer, 25 to 75 percent by weight of a second thermoplasticcomponent and about 5 to about 40 percent by weight zinc oxide. In amost preferred embodiment of the present invention, the intermediatelayer is formed from a blend of about 15 to about 25 percent by weightethylene methacrylic/acrylic acid copolymer, about 50 to about 60percent by weight of a second thermoplastic component and about 20 toabout 30 percent by weight zinc oxide. In another embodiment of theinvention, the second thermoplastic component is present in theintermediate layer blend in an amount of less than 50 percent by weight,and preferably 30 to 45 percent by weight. A specific example of thisembodiment is an intermediate layer composition including about 57percent by weight HYTREL® 3078, about 20 percent by weight NUCREL® 960,and about 23 percent by weight zinc oxide.

The intermediate layer blend preferably has a flexural modulus of lessthan about 10,000 psi, more preferably about 5,000 to about 8,000 psiand most preferably about 7,500 psi. Likewise, the intermediate layersemployed in the golf balls of the present invention preferably have aShore D hardness of about 35 to 50, more preferably about 37 to about 45and most preferably about 40.

Preferably, the intermediate layer and core construction employed in thepresent invention have a compression of less than about 65, morepreferably about 50 to about 65, and most preferably about 50 to 55.

The intermediate layer employed in the golf balls of the presentinvention preferably have a thickness from about 0.020 inches to about0.125 inches, more preferably about 0.035 inches to about 0.085 inchesand most preferably about 0.06 inches The outer diameter of theintermediate layer is preferably about 1.510 inches.

The golf balls of the present invention may include a plurality ofintermediate layers, e.g., a first intermediate layer adjacent the coreand a second intermediate layer adjacent the cover. The firstintermediate layer may include the materials as discussed above.Preferably, the first intermediate layer includes a thermoplasticmaterial and has a greater hardness than the core. The secondintermediate layer may be disposed around the first intermediate layerand preferably has a greater hardness than the first intermediate layer.

The second intermediate layer may be formed of materials such aspolyether or polyester thermoplastic urethanes, thermoset urethanes, andionomers such as acid-containing ethylene copolymer ionomers, includingE/X/Y terpolymers where E is ethylene, X is an acrylate ormethacrylate-based softening comonomer present in 0 to 50 weight percentand Y is acrylic or methacrylic acid present in 5 to 35 weight percent.More preferably, in a low spin rate embodiment designed for maximumdistance, the acrylic or methacrylic acid is present in 15 to 35 weightpercent, making the ionomer a high modulus ionomer.

In one embodiment, the second intermediate layer is formed ofcomposition including at least one high acid ionomer. As used herein,the term “high acid ionomer”, is an ionomer resin wherein Y is acrylicor methacrylic acid units present from about 17 weight percent to about35 weight percent in the polymer. Generally, a high acid ionomer willhave a Shore D hardness of about 60 or greater and a flexural modulus ofabout 50,000 psi or greater, preferably from about 50,000 psi to about125,000 psi. In the vernacular of the golf ball art, high acid ionomersare sometimes referred to as “hard” ionomers.

In another embodiment, the second intermediate layer is preferablyformed of a thermoset material, preferably having a flexural modulus ofabout 50,000 psi or greater. In one embodiment, the thermoset materialis polybutadiene.

In one embodiment, the second intermediate layer is adjacent the coverand has a hardness greater than that of the first intermediate layer.

A third intermediate layer may be disposed in between the first andsecond intermediate layers. The third intermediate layer may be formedof the variety of materials as discussed above. In one embodiment, thethird intermediate layer is disposed in between the first and secondintermediate layers and preferably has a hardness greater than thehardness of the first intermediate layer.

The Cover Layer

The cover layer of the present invention may include at least one layerof a thermoplastic or thermosetting material. Any number of a widevariety of cover materials may be used in the present invention such asionomer resins, polyurethanes, balata and blends thereof.

In one embodiment, the cover is formed of a composition including verylow modulus ionomers (VLMIs). As used herein, the term “very low modulusionomers”, or the acronym “VLMIs”, are those ionomer resins furtherincluding a softening comonomer X, commonly a (meth)acrylate ester,present from about 10 weight percent to about 50 weight percent in thepolymer. VLMIs are copolymers of an α-olefin, such as ethylene, asoftening agent, such as n-butyl-acrylate or iso-butyl-acrylate, and anα,β-unsaturated carboxylic acid, such as acrylic or methacrylic acid,where at least part of the acid groups are neutralized by a magnesiumcation. Other examples of softening comonomers include n-butylmethacrylate, methyl acrylate, and methyl methacrylate. Generally, aVLMI will have a flexural modulus from about 2,000 psi to about 10,000psi. VLMIs are sometimes referred to as “soft” ionomers. U.S. Pat. No.6,144,415, which is incorporated in its entirety by reference herein,discloses suitable VLMIs for incorporation into the cover formulationsof the present invention.

Ionomers, such as acid-containing ethylene copolymer ionomers, includeE/X/Y copolymers where E is ethylene, X is a softening comonomer such asacrylate or methacrylate present in 0 to 50 (preferably 0 to 25, mostpreferably 0 to 2), weight percent of the polymer, and Y is acrylic ormethacrylic acid present in 5 to 35 (preferably 10 to 35, mostpreferably 15 to 20) weight percent of the polymer, wherein the acidmoiety is neutralized 1 to 90 percent (preferably at least 40 percent,most preferably at least about 60 percent) to form an ionomer by acation such as lithium, sodium, potassium, magnesium, calcium, barium,lead, tin, zinc or aluminum, or a combination of such cations, lithium,sodium and zinc being the most preferred. Specific acid-containingethylene copolymers include ethylene/acrylic acid, ethylene/methacrylicacid, ethylene/acrylic acid/n-butyl acrylate, ethylene/methacrylicacid/n-butyl acrylate, ethylene/methacrylic acid/iso-butyl acrylate,ethylene/acrylic acid/iso-butyl acrylate, ethylene/methacrylicacid/n-butyl methacrylate, ethylene/acrylic acid/methyl methacrylate,ethylene/acrylic acid/methyl acrylate, ethylene/methacrylic acid/methylacrylate, ethylene/methacrylic acid/methyl methacrylate, andethylene/acrylic acid/n-butyl methacrylate. Preferred acid-containingethylene copolymers include ethylene/methacrylic acid, ethylene/acrylicacid, ethylene/methacrylic acid/n-butyl acrylate, ethylene/acrylicacid/n-butyl acrylate, ethylene/methacrylic acid/methyl acrylate andethylene/acrylic acid/methyl acrylate copolymers. The most preferredacid-containing ethylene copolymers are ethylene/methacrylic acid,ethylene/acrylic acid, ethylene/(meth)acrylic acid/n-butyl acrylate,ethylene/(meth)acrylic acid/ethyl acrylate, and ethylene/(meth)acrylicacid/methyl acrylate copolymers.

As mentioned above, ionomer resins are commercially available from E.I.DuPont de Nemours and Co. of Wilmington, Del., under the tradenameSURLYN®, and from Exxon Corporation of Houston, Tex., under thetradename IOTEK®. Some particularly suitable SURLYNS® include SURLYN®8140 (Na) and SURLYN® 8546 (Li) which have an methacrylic acid contentof about 19 percent.

To aid in the processing of the cover stock, and as is well known in theart, ionomer resins may be blended in order to obtain a cover havingdesired characteristics. For this reason, it is preferable that thecovers of the golf balls of the present invention be formed from a blendof two or more ionomer resins. A particularly preferred cover materialfor use in the present invention is formed from a blend of about 50percent by weight SURLYN® 7940, about 47 percent by weight SURLYN® 8940and about 3 percent by weight SURLYN® 8660.

In one embodiment, the cover material includes a blend of a very softmaterial and a harder material. Preferably, the cover includes about 75to about 25 parts by weight based on 100 parts by weight resin (pph) ofa VLMI and about 25 pph to about 75 pph of a standard ionomer resin.Preferably, the VLMI is a sodium ionomer resin and constitutes about 40pph to about 60 pph of the ionomer blend and the standard ionomer resinis a lithium ionomer resin and constitutes about 60 pph to about 40 pphof the ionomer blend. Even more preferably, a 50/50 blend of the sodiumand lithium ionomers with additives, e.g., color concentrate, is usedfor the cover composition. Suitable sodium ionomer resins include, butare not limited to SURLYN® 8320, SURLYN® 8269, and SURLYN® 8265.

The sodium ionomer resin is preferably a copolymer including about 95 toabout 80 parts by weight of copolymer of ethylene and about 5 to about12 parts by weight of the copolymer of acrylic or methacrylic acid inwhich about 10 percent to about 90 percent of the acid groups areneutralized by sodium. In one embodiment, the sodium ionomer resin usedin the present invention has a flexural modulus between about 1,000 andabout 20,000 psi (5 and 140 MPa) and, more preferably, between about2,000 and about 10,000 psi (10 to 70 MPa).

The lithium ionomer resin is preferably a copolymer including about 95to about 80 parts by weight of ethylene and about 10 to about 16 partsby weight of acrylic or methacrylic acid based on 100 parts by weightcopolymer. Preferably, the lithium ionomer resin has about 10 percent toabout 90 percent of the acid groups neutralized by lithium. Preferably,the lithium ionomer resin has a high flexural modulus which is aboveabout 60,000 psi (415 MPa). More preferably, the lithium ionomer resinused in the present invention has a flexural modulus between about60,000 and about 80,000 psi (415 and 550 MPa). Good results have beenobtained with the lithium ionomer resins having flexural moduli in therange of about 60,000 psi to about 70,000 psi (415 to 485 MPa), e.g.,SURLYN® 8118, SURLYN® 7930 and SURLYN® 7940.

Both the lithium and sodium ionomer resins preferably have about 10percent to about 90 percent of their carboxylic acid groups neutralizedby their respective metal ions. More preferably, both the lithium andsodium ionomer resins have their carboxylic acid groups neutralizedabout 35 percent to about 65 percent by the metal ion. Preferably, theVLMI and harder ionomer resins include the same monocarboxylic acid,e.g. either methacrylic or acrylic acid.

In order to adjust the characteristics of the cover stock, other ionomerresins besides sodium and lithium can be employed.

SURLYN® 8320, SURLYN® 8269 and SURLYN® 8265 have flexural moduli of2,800 psi (20 MPa), 2,800 psi (20 MPa) and 7,100 psi (50 MPa),respectively. SURLYN® 8118, 7930 and 7940 have flexural moduli of 61,000psi (420 MPa), 67,000 psi (460 MPa) and 61,000 psi (420 MPa)respectively.

Conventionally, ionomer resins with different melt flow indexes areemployed to obtain the desired characteristics of the cover stock.SURLYN® 8118, 7930 and 7940 have melt flow indices of about 1.4, 1.8,and 2.6 g/10 min., respectively. SURLYN® 8269 and SURLYN® 8265 both havea melt flow index of about 0.9 g/10 min. Preferably, the blend ofionomer resins used to make a cover of a golf ball in accordance withthe present invention has a melt flow index between about 1 to about 4g/10 min. and, more preferably, about 1 to about 3 g/10 min.

The combined amount of lithium ionomer resin and sodium ionomer resinused to make a cover in accordance with this embodiment of the presentinvention as described generally makes up at least about 90 percent byweight of the total weight of the golf ball cover and, preferably, atleast about 95 percent by weight. Additional materials which may beincluded in the golf ball cover are other SURLYN® resins; whiteningagents such as titanium dioxide; dyes; UV absorbers; opticalbrighteners; and other additives which are conventionally included ingolf ball covers.

In another embodiment, the cover composition includes at least twoionomer resins, preferably sodium ionomer resin and lithium ionomerresin, having similar flexural moduli. Preferably, the sodium ionomerresin is a copolymer including about 95 to about 80 parts by weight ofcopolymer of ethylene and about 12 to about 20 parts by weight of thecopolymer of acrylic or methacrylic acid in which about 10 percent toabout 90 percent of the acid groups are neutralized by sodium.

Preferably, the lithium ionomer resin is a copolymer including about 95to about 80 parts by weight of ethylene and about 12 to about 20 partsby weight of acrylic or methacrylic acid based on 100 parts by weightcopolymer. Preferably, the lithium ionomer resin has about 10 percent toabout 90 percent of the acid groups neutralized by lithium.

Preferably, the sodium ionomer resin used in the present invention has aflexural modulus between about 60,000 and about 80,000 psi (415 and 550MPa).

The lithium ionomer resin used in the present invention has a flexuralmodulus between about 60,000 and about 80,000 psi (415 and 550 MPa).Good results have been obtained with the sodium and lithium ionomerresins having flexural moduli in the range of about 60,000 psi to about70,000 psi (415 to 485 MPa).

Preferably, the ionomer resins incorporate the same monocarboxylic acid,e.g., either methacrylic or acrylic acid.

Sodium ionomer resin sold by DuPont under the name SURLYN® 8920 hasworked well in the present invention. Good results have also beenobtained with a lithium ionomer resin sold under the trade name SURLYN®7940 by DuPont.

The cover layer employed in the present invention preferably have aShore D hardness of about 60 to about 72, more preferably about 65 toabout 70 and most preferably about 68 to about 70.

Castable reactive liquid materials are particularly preferred for thecover layers of the balls of the present invention. As used herein, theterm “castable reactive liquid material” may refer to thermoset orthermoplastic materials. In a preferred embodiment, the castablereactive liquid material is a thermoset material.

In one embodiment, the castable reactive liquid material is casturethane or polyurethane. Polyurethane is a product of a reactionbetween a polyurethane prepolymer and a curing agent. The polyurethaneprepolymer is a product formed by a reaction between a polyol and adiisocyanate. Often a catalyst is employed to promote the reactionbetween the curing agent and the polyurethane prepolymer. In the case ofcast polyurethanes, the curing agent is typically either a diamine orglycol.

In another preferred embodiment, the castable reactive liquid materialis a thermoset cast polyurethane. Thermoset cast polyurethanes aregenerally prepared using a diisocyanate, such as 2,4-toluenediisocyanate (TDI), methylenebis-(4-cyclohexyl isocyanate) (HMDI), orpara-phenylene diisocyanate (“PPDI”) and a polyol which is cured with apolyamine, such as methylenedianiline (MDA), or a trifunctional glycol,such as trimethylol propane, or tetrafunctional glycol, such asN,N,N′,N′-tetrakis(2-hydroxpropyl)ethylenediamine. However, any suitablecast or non-cast thermoset polyurethane may be employed to form outercover layers of the present invention.

Other suitable thermoset materials contemplated for the cover layersinclude, but are not limited to, thermoset urethane ionomers andthermoset urethane epoxies. Examples of suitable thermoset polyurethaneionomers are disclosed in U.S. Pat. Nos. 5,334,673 and 5,692,974, whichare incorporated in their entirety by reference herein. Other examplesof thermoset materials include polybutadiene, natural rubber,polyisoprene, styrene-butadiene, or styrene-propylene-diene rubber,which are particularly suitable when used in an intermediate layer of agolf ball.

When the cover includes more than one layer, e.g., an inner cover layerand an outer cover layer, various constructions and materials aresuitable. For example, as disclosed in U.S. Pat. Nos. 5,803,831 and6,210,293, which are incorporated in their entirety by reference herein,an inner cover layer may surround the intermediate layer with an outercover layer disposed thereon or an inner cover layer may surround aplurality of intermediate layers.

When using an inner and outer cover layer construction, the outer coverlayer material is preferably a thermoset material that includes at leastone of a castable reactive liquid material and reaction productsthereof, as described above, and preferably has a hardness from about 30Shore D to about 60 Shore D. In one embodiment, the outer cover layer isthin, preferably less than about 0.05 inches, and more preferably fromabout 0.02 inches to about 0.045 inches.

The inner cover layer may be formed from a wide variety of hard (about65 Shore D or greater, preferably from about 69 Shore D to about 74Shore D), high flexural modulus resilient materials, which arecompatible with the other materials used in the adjacent layers of thegolf ball. The inner cover layer materials preferably has a flexuralmodulus of about 65,000 psi or greater. In one embodiment, the flexuralmodulus of the inner cover layer material is from about 70,000 psi toabout 120,000 psi.

Suitable inner cover layer materials include the hard, high flexuralmodulus ionomer resins and blends thereof as disclosed in U.S. Pat. No.5,885,172, which is incorporated in its entirety by reference herein.These ionomers are obtained by providing a cross metallic bond topolymers of monoolefin with at least one member selected from the groupconsisting of unsaturated mono- or di-carboxylic acids having 3 to 12carbon atoms and esters thereof (the polymer contains 1 to 50 percent byweight of the unsaturated mono- or di-carboxylic acid and/or esterthereof). More particularly, such acid-containing ethylene copolymerionomer component includes E/X/Y copolymers where E is ethylene, X is asoftening comonomer such as acrylate or methacrylate present in 0-50(preferably 0-25, most preferably 0-20), weight percent of the polymer,and Y is acrylic or methacrylic acid present in 5-35 (preferably atleast about 16, more preferably at least about 16-35, most preferably atleast about 16-20) weight percent of the polymer, wherein the acidmoiety is neutralized 1-90 percent (preferably at least 40 percent, mostpreferably at least about 60 percent) to form an ionomer by a cationsuch as lithium*, sodium*, potassium, magnesium*, calcium, barium, lead,tin, zinc* or aluminum (*=preferred), or a combination of such cations.Specific acid-containing ethylene copolymers include ethylene/acrylicacid, ethylene/methacrylic acid, ethylene/acrylic acid/n-butyl acrylate,ethylene/methacrylic acid/n-butyl acrylate, ethylene/methacrylicacid/iso-butyl acrylate, ethylene/acrylic acid/iso-butyl acrylate,ethylene/methacrylic acid/n-butyl methacrylate, ethylene/acrylicacid/methyl methacrylate, ethylene/acrylic acid/methyl acrylate,ethylene/methacrylic acid/methyl acrylate, ethylene/methacrylicacid/methyl methacrylate, and ethylene/acrylic acid/n-butylmethacrylate. Preferred acid-containing ethylene copolymers includeethylene/methacrylic acid, ethylene/acrylic acid, ethylene/methacrylicacid/n-butyl acrylate, ethylene/acrylic acid/n-butyl acrylate,ethylene/methacrylic acid/methyl acrylate and ethylene/acrylicacid/methyl acrylate copolymers. The most preferred acid-containingethylene copolymers are ethylene/methacrylic acid, ethylene/acrylicacid, ethylene/(meth)acrylic acid/n-butyl acrylate,ethylene/(meth)acrylic acid/ethyl acrylate, and ethylene/(meth)acrylicacid/methyl acrylate copolymers.

Examples of other suitable inner cover materials include thermoplasticor thermoset polyurethanes, polyetheresters, polyetheramides, orpolyesters, dynamically vulcanized elastomers, functionalizedstyrene-butadiene elastomers, metallocene polymers, polyamides such asnylons, acrylonitrile butadiene-styrene copolymers (ABS), or blendsthereof. Suitable thermoplastic polyetheresters include materials whichare commercially available from DuPont under the tradename Hytrel®.Suitable thermoplastic polyetheramides include materials which areavailable from Elf-Atochem under the tradename Pebax®.

The multi-layer golf ball of the invention can have an overall diameterof any size. Although the United States Golf Association specificationslimit the minimum size of a competition golf ball to 1.680 inches indiameter or more, there is no specification as to the maximum diameter.Moreover, golf balls of any size can be used for recreational play. Thepreferred diameter of the present golf balls is from about 1.680 inchesto about 1.800 inches. The more preferred diameter is from about 1.680inches to about 1.760 inches. The most preferred diameter is about 1.680inches to about 1.740 inches.

The golf balls of the present invention have an overall maximumcompression of about 85, preferably about 75 to about 85, morepreferably about 80 to about 85 and most preferably about 82.

Golf Ball Assembly

The center 11, as shown in FIG. 1, is preferably formed by compressionmolding a sphere from a prep of center material. Compression moldingsolid centers is well known in the art.

In one embodiment, the golf ball of the present invention may be formedwith a laminate process, as shown in FIGS. 2 and 3. In order to formmultiple layers around the center according to this embodiment of theinvention, a laminate 20 is first formed. The laminate 20 includes atleast two layers and, preferably, three layers 22, 23, 24. In oneembodiment, the laminate is formed by mixing uncured core material to beused for each layer and calendar rolling the material into thin sheets32, 33, 34. In another embodiment, the laminate is formed by mixinguncured intermediate layer material and rolling the material into sheets32, 33, 34. The laminate sheets 32, 33, 34 are stacked together to formthe laminate 20 having three layers 22, 23, 24 using calender rollingmills. In another embodiment, however, the sheets 32, 33, 34 are made byextrusion.

In an alternate embodiment, the laminate 20 can be further constructedusing an adhesive between each layer of material. Preferably, an epoxyresin such as Epoxy Resin #1028 from RBC Industries in Warwick, R.I. isused. The adhesive should have good shear and tensile strength and,preferably the adhesive should have a tensile strength over about 1500psi. Still further, the adhesive should not become brittle when cured.An adhesive having a Shore D hardness of less than 60 when cured ispreferred. The adhesive layer applied to the sheets should be very thinand preferably, less than 0.004 inches thick.

Preferably, each laminate sheet is formed to a thickness that isslightly larger than the thickness of the layers 12, 13, 14 in thefinished golf ball 10. Each of these thicknesses can be varied, but allhave a thickness of preferably less than about 0.1 inches. Preferably,the sheets are formed to thicknesses that are less than 0.05 inches andthe laminate thickness is less than 0.15 inches. The sheets 32, 33 and34 should have very uniform thicknesses, i.e., the thickness of eachsheet should not vary more than about 0.005 inches.

The next step in the method, as shown in FIGS. 4-7, is to form multiplelayers around the center. This is preferably accomplished by placing twolaminates 20, 21 in between a top mold 36 and a bottom mold 37, asillustrated in FIG. 4. The molds 36, 37 are formed of mold frames 38 andreplaceable mold halves 39 such as that described in U.S. Pat. No.4,508,309 to Brown, the disclosure of which is incorporate in itsentirety by reference herein. The laminates 20, 21 are formed to thecavities in the mold halves 39.

In one embodiment, the laminates 20, 21 are cut into patterns that, whenjoined, form a laminated layer around the center 11. For example, asillustrated in FIG. 5, the laminates 20, 21 may be cut into FIG.8-shaped or barbell-like patterns, similar to a baseball or a tennisball cover. Other patterns, such as curved triangles, hemisphericalcups, ovals, or any like patterns that may be joined together to form alaminated layer around the center 11 may also be used. The patterns maythen be placed in between molds 36, 37 and formed to the cavities in themold halves 39.

In one embodiment, the laminates are suction formed to the cavities byusing a vacuum source 40. The vacuum source 40 suction forms thelaminates 20, 21 to the half mold cavities 39 so that uniformity inlayer thickness is maintained.

After the laminates 20, 21 have been formed to the cavities, centers 11are then inserted between the laminates, as shown in FIG. 6. Thelaminates 20, 21 are then compression molded about the center 11 underconditions of temperature and pressure that are well known in the art.

The half molds 39 have a plurality of vents 41, as shown in FIGS. 7 and8. The compression molding step includes flowing excess layer materialfrom the laminates 20, 21 through at least three vents 41 so that theflow of laminate material is symmetrical about the center 11 and so thatthe center 11 does not shift due to lateral flow patterns. In apreferred embodiment, the half molds 39 have 4 to 6 vents.

The next step in the present invention is to form a cover 15 around thegolf ball core 16, i.e., the inner components of the golf ball. The core16, including center 11 and layers 12, 13, 14, is supported within apair of cover mold-halves 50, 51 by a plurality of retractable pins 52,as shown in FIG. 9. The retractable pins 52 are actuated by conventionalmeans known to those of ordinary skill in the art of mold design.

After the mold-halves 50, 51 are closed together with the pins 52supporting the core 16, the cover material is injected into the mold ina liquid state through a plurality of injection ports or gates 49, asshown in FIG. 10. Gates 49 can be edge gates or sub-gates. With edgegates, the resultant golf balls are all interconnected and may beremoved from the mold-halves 50, 51 together in a large matrix.Sub-gating automatically separates the mold runner from the golf ballsduring the ejection of the golf balls from mold-halves 50, 51.

As illustrated in FIG. 11, retractable pins 52 are retracted after apredetermined amount of cover material has been injected into themold-halves 50, 51. The predetermined amount of cover material issubstantially all of the material to be injected. Thus, the core 16 issubstantially surrounded by cover material and does not shift when theretractable pins 52 are removed. This allows the liquid cover materialto flow and substantially fill the cavity between the core 16 and themold-halves 50, 51. At the same time, concentricity is maintainedbetween the core 16 and the mold-halves 50, 51.

The cover material is allowed to solidify around the core 16, therebyforming cover 15. Golf ball 10 is then ejected from mold-halves 50, 51,and finished using processes which are well known in the art. Thetemperatures and curing time for mold-halves 50, 51 are generally knownin the art and are dependent on the material that is being used forcover 15.

In another embodiment, shown in FIG. 12, the cover 15 is formed usingcover layer hemispheres 55, 56. Two cover layer hemispheres 55, 56 arepre-formed of the desired cover material, preferably, by an injectionmolding process. The hemispheres 55, 56 are positioned around the core16, thereby forming an assembly 57. Assembly 57 is placed into acompression mold 58 that includes two compression mold-halves 53, 54.Mold-halves 53, 54 are advanced toward each other until their matingsurfaces touch, and the mold 58 is heated to melt the hemispheres.Mold-halves 53, 54 compress and heat the hemispheres 55, 56 about thecore 16 to mold the cover material thereto.

While the embodiments above are directed to the use of laminates to formthe golf balls of the present invention, the construction of the golfballs of the present invention are not limited to the embodimentsdescribed above and can be made by any conventional processes employedin the golf ball art. For example, the solid cores can be eitherinjection or compression molded. The intermediate layer may then besubsequently injection or compression molded about the core. It isimportant that the intermediate layer material be able to sustain thetemperatures applied during the application of the cover layer. Thecover layer or layers may then be injection or compression molded orcast about the intermediate layer.

Specific Golf Ball Constructions

Various embodiments of the golf balls are outlined below. The golf ballsof the invention, however, variation of these embodiments are covered aswell. Properties such as hardness, Bayshore resilience, flexuralmodulus, center diameter, and layer thickness of the golf balls of thepresent invention have been found to affect play characteristics such asspin, initial velocity and feel of golf balls.

In one embodiment, the center 11 and each of the layers 12, 13, 14 areformed of a thermoset rubber, such as polybutadiene rubber. In thisembodiment, a golf ball core 16 has a center 11 and three layers 12, 13and 14. The center diameter should be greater than about 1 inch and,preferably, should be about 1.25 to 1.45 inches. The most preferredcenter has a diameter of about 1.4 inches. Each of the layerssurrounding the center should have a thickness of less than about 0.1inches and preferably, less than about 0.05 inches. The most preferredthickness of the layers is about 0.03 to about 0.05 inches where thethickness of the third layer is equal to or less than the thickness ofthe first and second layers. Moreover, the center 11 of the golf ballpreferably has an outer diameter of greater than 60 percent of thefinished ball 10 diameter. Most preferably, the center 11 has a diameterthat is at least 75 percent of the diameter of the finished ball 10.

A small center of 1 inch or less and relatively thick core layers, eachhaving a thickness of greater than 0.1 inches, decreases ball initialvelocity and reduces the ball spin rate effects. When impacting a golfball with different clubs within a set, the impact speed and the impactangle are changed. On an average, for a tour professional the impactspeed of a driver is about 110 miles an hour. The average professional 5iron impact speed is around 90 miles an hour and the wedge impactvelocity is less than about 80 miles an hour. Moreover, the force on thegolf ball must be broken up into two components, the normal force thatis normal to the club face and the tangential force that is parallel tothe club face. Since most professionals use a driver having a loft ofabout 10 degrees, the tangential force is significantly less than thenormal force. However, when using a wedge having a loft between 48 and60 degrees, the tangential force becomes very significant. For example,experimental data shows that with a clubhead having an impact velocityof about 95 miles an hour and an angle of 20 degrees, a two piece ballhas a maximum deflection of about 0.151 inches. When hit with a clubheadat 95 miles an hour and an impact angle of 40 degrees, the ball has amaximum deflection of about 0.128 inches or a difference of 0.023inches. Thus, the impact deflection depends significantly on the impactangle, and by having outer layers of less than 0.1 inches, the spincharacteristics of the ball is altered for different clubs within a setas discussed in more detail below.

For a high spin rate ball that also has good driver trajectorycharacteristics, the center 11 of the golf ball should have a Shore Chardness of about 70 or less. The first layer 12 should be harder thanthe center 11 and should have a Shore C hardness of about 70 to about75. The second layer 13 should be harder than the first layer 12 andhave a Shore C hardness of about 72 to about 77. The third layer orouter layer 14 should be harder than the second layer 13 and have aShore C hardness of about 75 to about 80. The cover 15 of the firstembodiment golf ball should be a soft cover and have a Shore D of lessthan 60. Moreover, the center 11, layers 12, 13 and 14 and the cover 15should be configured to provide a golf ball compression of less than 85and more preferably, less than about 80.

By creating a core 16 with relatively thin outer layers thatprogressively get harder, the spin rate of the ball is surprisingly goodfor a player that desires a high spin rate golf ball. More particularly,when this type of player hits the ball with a short iron, only the outerlayer and cover affect the spin rate of the ball. By incorporating avery hard core outer layer and a soft cover, the spin rate is maximizedfor the short iron shot such as a wedge having an angle of about 48 to60 degrees. In order to reduce the spin rate a little for middle ironshots such as a 6 iron having aloft of about 32 degrees to make surethat sufficient distance is obtained, the second layer is softer thanthe third layer. Similarly, to decrease the spin rate, provide gooddistance and a good trajectory for long irons such as a 3 iron having aloft of about 20 degrees, the first layer 11 is softer than the secondlayer 12. Finally, for a low spin rate with the driver having a loft ofabout 8 to 12 degrees, the center is made very soft.

Solid cores having diameters of about 1.58 inches may also be made usingthe compositions of the core materials outline above. Cores having thecenters as defined above preferably have a compression of about 50. Thefirst layer composition preferably has a compression of about 75.Preferably, the first layer material will have a compression that isover 25 percent greater than the center material compression. The secondlayer composition preferably has a compression of about 85 and, thus,has a greater compression than the first layer. The third layercomposition has a compression of about 110, which is significantlygreater than the second layer. Preferably, the third layer compressionis more than 75 percent greater than the center material compression.

In a preferred embodiment, the cover material includes a blend of twomaterials, a very soft material and a harder material. Preferably, thecover includes about 75 to about 25 parts by weight based on 100 partsby weight resin (phr) of a low flexural modulus ionomer resin; and about25 to about 75 pph of a standard ionomer resin. The low flexural modulusionomer is preferably a sodium ionomer resin and constitutes about 40pph to about 60 pph of the ionomer blend and the standard flexuralionomer is a lithium ionomer resin and constitutes about 60 pph to about40 pph of the ionomer blend. The sodium ionomer resin is preferably acopolymer including about 95 to about 80 parts by weight of copolymer ofethylene and about 5 to about 12 parts by weight of the copolymer ofacrylic or methacrylic acid in which about 10% to about 90% of the acidgroups are neutralized by sodium. Preferably, lithium ionomer resin is acopolymer including about 95 to about 80 parts by weight of ethylene andabout 10 to about 16 parts by weight of acrylic or methacrylic acidbased on 100 party by weight copolymer. Preferably, the lithium ionomerresin has about 10 percent to about 90 percent of the acid groupsneutralized by lithium.

Preferably, the low flexural modulus sodium ionomer resin used in thisembodiment has a flexural modulus between about 1,000 psi and about20,000 psi (5 MPa and 140 MPa) and, more preferably, between about 2,000psi and about 10,000 psi (10 MPa to 70 Mpa). The lithium ionomer resinpreferably has a high flexural modulus which is above about 60,000 psi(415 MPa). More preferably, the lithium ionomer resin used in thepresent invention has a flexural modulus between about 60,000 and about80,000 psi (415 and 550 MPa). Good results have been obtained with thelithium ionomer resins having flexural moduli in the range of about60,000 psi to about 70,000 psi (415 to 485 MPa).

In this embodiment, both the lithium and sodium ionomer resinspreferably have about 10 percent to about 90 percent of their carboxylicacid groups neutralized by their respective metal ions. More preferably,both the lithium and sodium ionomer resins have their carboxylic acidgroups neutralized about 35% to about 65% by the metal ion.

In addition, the ionomer resins preferably include the samemonocarboxylic acid, e.g. either methacrylic or acrylic acid.

In one embodiment, 55 weight percent SURLYN® 8320 and 45 weight percentSURLYN® 7940 are included in the cover blend, wherein the blend has ahardness of 55 Shore D. In another embodiment, 45 weight percent SURLYN®8320 and 55 weight percent SURLYN® 7940 are included in the cover blendwith a hardness of 59 Shore D.

In a second embodiment, the center 11 and each of the layers 12, 13, 14also include a thermoset rubber, such as polybutadiene.

In this second embodiment, the golf ball core also has a center 11 andthree layers 12, 13, 14. The center 11 should be greater than 1.0 inchand, preferably, about 1.25 to 1.45 inches in diameter. The mostpreferred center has a diameter of about 1.4 inches. Each of the layersshould have a thickness of less than about 0.1 inches and preferably,less than about 0.05 inches. The most preferred thickness of each of thelayers is about 0.03 inches. Again, by having outer layers of less than0.1 inches, the spin characteristics of the ball can be altered fordifferent clubs within a set.

The center 11 of the second embodiment golf ball should have a Shore Chardness of greater than about 75 for low swing speed players. The firstlayer should be softer than the center and have a Shore C hardness ofabout 75 to 72. The second layer should be softer than the first layerand have a Shore C hardness of about 73 to 70. The third layer should bethe softest and have a Shore C hardness of less than about 70. The coverof the second embodiment golf ball should have good resilience anddurability. Preferably, the cover of the second embodiment is a hardercover and includes a blend of about 50/50 by weight of two standard orhigh acid ionomers. Standard ionomers have about 15 parts by weight ofacrylic or methacrylic acid. High acid ionomers have about 17 or moreparts by weight of acrylic or methacrylic acid.

By creating a golf ball core 16 with relatively thin outer layers thatprogressively get softer, the feel and distance is optimized for a lowswing speed player. More particularly, when the low swing speed playerhits the ball with a short iron, only the outer or third layer and coverare compressed. By utilizing a soft core and a harder cover, the feel ofthe ball is relatively soft when compared to distance balls having hardcovers and hard cores. In order to increase the distance for middleirons while still providing a relatively soft feel, the second layer ismade harder than the third layer. Similarly, to provide greaterresiliency for long irons, the first layer 11 is harder than the secondlayer. Finally, for maximum resiliency with the driver, the center ismade harder than each of the layers. Since the center 11 is large, i.e.,between about 1.25 and 1.45 inches in diameter, the ball has a highcompression and initial velocity. However, since the third layer issoft, the ball provides a surprisingly better feel than hard core/hardcover balls.

Preferably, the cover material of this embodiment should provide goodresiliency and durability. In one embodiment, the cover materialincludes of a blend of two ionomer resins having relatively the sameflexural moduli, e.g., sodium ionomer resin and lithium ionomer resin.

Preferably, the sodium ionomer resin is a copolymer including about 95to about 80 parts by weight of copolymer of ethylene and about 12 toabout 20 parts by weight of the copolymer of acrylic or methacrylic acidin which about 10 percent to about 90 percent of the acid groups areneutralized by sodium.

The lithium ionomer resin is preferably a copolymer including about 95to about 80 parts by weight of ethylene and about 12 to about 20 partsby weight of acrylic or methacrylic acid based on 100 parts by weightcopolymer. Preferably, the lithium ionomer resin has about 10 percent toabout 90 percent of the acid groups neutralized by lithium.

Preferably, the sodium ionomer resin used according to this embodimentpreferably has a flexural modulus between about 60,000 and about 80,000psi (415 and 550 Mpa). The lithium ionomer resin used according to thisembodiment preferably has a flexural modulus between about 60,000 andabout 80,000 psi (415 and 550 MPa). Good results have been obtained withthe sodium and lithium ionomer resins having flexural moduli in therange of about 60,000 psi to about 70,000 psi (415 to 485 MPa).

Preferably, the ionomer resins incorporate the same monocarboxylic acid,e.g., either methacrylic or acrylic acid.

Sodium ionomer resin sold by DuPont under the name SURLYN® 8920 hasworked well in the present invention. Good results have also beenobtained with a lithium ionomer resin sold under the trade name SURLYN®7940 by DuPont.

The golf ball of the present invention can have an overall diameter ofany size. Although the United States Golf Association (USGA)specifications limit the minimum size of a competition golf ball to morethan 1.680 inches in diameter, there is no specification as to themaximum diameter. Moreover, golf balls of any size can be used forrecreational play. The preferred diameter of the present golf balls isfrom about 1.680 inches to about 1.800 inches. The more preferreddiameter is from about 1.680 inches to about 1.760 inches. The mostpreferred diameter is about 1.680 inches to about 1.740 inches.

EXAMPLES Example 1

Table 1 sets forth an example of the core contents, i.e., center andinner layers, according to one embodiment of the invention. The fillersused in the compositions of these examples are regrind and bariumsulfate (BaSO4). Vulcup 40KE® and Varox 231 XL® are free radicalinitiators, and are a-a bis (t-butylperoxy) diisopropylbenzene and1,1-di (t-butylperoxy) 3,3,5-trimethyl cyclohexane, respectively.

TABLE 1 Core Compositions (pph, based on 100 parts of polybutadiene)Layer No. Center 1 2 3 Polybutadiene 100 100 100 100 Polywate 325 26 2318 13 Vulcup 40KE ® 0.3 0.3 0.3 0.3 Varox 231XL ® 0.6 0.5 0.5 0.5 BaSO₄31 26 25 25 Zinc Diacrylate 30 32 35 47 SR-350 2 2 2 6 Calcium Oxide 3 00 0 Zinc Oxide 0 3 6 6

The center 11 set forth in Table 1, has a Shore C hardness of about 65at the center point thereof and a Shore C hardness of about 68 at themidpoint between the center and the outer edge. The first layer 12 isharder than the center 11 and has a Shore C hardness of about 71. Thesecond layer 13 is harder than the first layer 12 and has a Shore Chardness of about 73. The third layer or outer layer 14 is harder thanthe second layer 13 and had a Shore C hardness of about 77. The cover 15of the first embodiment golf ball is a soft cover and includes a blendof about 50/50 by weight of very low flexural modulus ionomer and astandard ionomer. The golf ball preferably has a compression of about60.

The center 11 of the core 16 was compression molded to a diameter ofabout 1.39 inches and each of the three layers, 12, 13 and 14 had athickness of about 0.03 inches. Solid cores having diameters of about1.58 inches were made using the compositions of the core materials ofTable 1.

Cores having the center composition of Table 1 have a compression ofabout 50. The first layer composition has a compression of about 75. Thefirst layer material has a compression that is over 25 percent greaterthan the center material compression. The second layer composition has acompression of about 85 and, thus, has a greater compression than thefirst layer. The third layer composition has a compression of about 110,which is significantly greater than the second layer. The third layercompression is more than 75 percent greater than the center materialcompression.

All the ingredients except the peroxides were mixed in a Process LabBrabender mixer to about 180-200° F. The peroxides were added in thesecond stage to the initial mixture, and the resulting mixture wasremoved from the Brabender and blended on a lab mill to insurehomogeneity. After mixing, the mixture was then hand rolled using alaboratory mill and cut into pieces or “preps”. To make the centers 11,the preps were then compression molded at about 160° C. (320° F.) forabout 15 minutes. To fabricate the outer layers, the polybutadienerubber material was rolled into flat sheets and the sheets were stackedto form a laminate. The laminate was then compression molded around thecenters as described above. To form the finished golf balls, the coreswere ground and inserted into two cover hemispheres of lithium-sodiumblends of SURLYN®.

The cover blends used in this example is set forth in Table 2.

TABLE 2 Cover Compositions (pph) Example No. 1 2 SURLYN 8320 55% 45%SURLYN 7940 45% 55% Blend Hardness (Shore D) 55 59

Example 2

The center of the second embodiment, as set forth in Table 3, has aShore C hardness of about 77. The first layer is softer than the centerand has a Shore C hardness of about 73. The second layer is softer thanthe first layer and has a Shore C hardness of about 71. The third layeris softer than the second layer and has a Shore C hardness of about 68.The cover of the second embodiment golf ball is a harder cover than thatused with the first embodiment and includes a blend of about 50/50 byweight of a standard sodium ionomer and a standard lithium ionomer. Thecover, as described in Table 4, has a Shore D hardness of about 65 to70.

Table 3 sets forth the contents of the golf ball core in the secondembodiment. The compositions used to prepare the golf ball core of thisembodiment are all in parts per hundred (pph), based on 100 parts ofpolybutadiene.

In the second embodiment, the center 11 of the core 16 was compressionmolded to a diameter of about 1.39 inches and each of the three layers,12, 13 and 14 had a thickness of about 0.03 inches.

TABLE 3 Inner Ball Compositions (pph, based on 100 parts ofpolybutadiene) Layer No. Center 1 2 3 Polybutadiene 100 100 100 100Polywate 325 13 18 23 26 Vulcup 40KE ® 0.3 0.3 0.3 0.3 Varox 231XL ® 0.50.5 0.5 0.6 BaSO4 25 25 26 31 Zinc Diacrylate 47 35 32 30 SR-350 6 2 2 2Calcium Oxide 0 0 0 3 Zinc Oxide 6 6 3 0

To make the core centers 11, preps were made and compression molded. Tofabricate the outer layers, the polybutadiene rubber material was rolledinto flat sheets and stacked into a laminate. The laminate was thencompression molded around the centers as described above. To form thefinished golf balls, the cores were ground and inserted into two coverhemispheres of standard lithium-sodium blends of SURLYN®.

Example 3

Table 4 below provides batch compositions for intermediate layer blendsfor forming the novel multilayer golf balls of the present invention.However, it is to be understood that the examples are only forillustrative purposes and in no manner is the present invention limitedto the specific disclosures therein.

In particular, batch numbers 2-4 provide intermediate layer blendsincluding NUCREL® 960, HYTREL® 3078, and ZnO used to form theintermediate layers of the golf balls of the present invention. Batchnumber 1 provides a control intermediate layer blend.

TABLE 4 Intermediate Layer Formulations Flexural % NUCREL ® % HYTREL ®Modulus Specific Batch # 960 3078 % ZnO (psi) Gravity 1 — 80 20 42101.27 2 10 75 15 5560 1.21 3 20 70 10 7710 1.17 4 30 65 5 7250 1.14

Example 4

Multilayer golf balls were made having intermediate layers formed fromthe batch compositions set forth in Table 4. Several dozen golf ballswere formed using each batch composition and subsequently tested forcompression, spin rate and initial velocity.

The cores of all of the multilayer balls were formed by compressionmolding a blend of the batch formulation set forth in Table 5 below. Allof the cores had a diameter of 1.39 inches and were measured to havecompressions ranging from about 45 to about 55 and specific gravities offrom about 1.134 to about 1.146.

The intermediate layer blends of Table 4 were subsequently injectionmolded about the cores to form the intermediate layers of the ballshaving an outer diameter of about 1.51 inches.

TABLE 5 Core Formulation Material Parts Per Hundred Polybutadiene (Shell1220) 76.0 Rubber (Enichem Br40) 24.0 Pigment 0.10 Zinc Diacrylate 24.79Calcium Oxide 2.16 Regrind 6.47 Peroxide (VAROX ®) 0.43 Peroxide (EF-60)(DBDB) 0.16 Filler 22.64

All of the multilayer balls had a cover composition formed by injectionmolding a blend including 50 percent SURLYN® 7940 and 50 percent SURLYN®8140 about the intermediate layers and were subsequently finished usingconventional clear coating and buffing techniques. The finished golfballs had an outer diameter of about 1.68 inches. These balls weretested for initial velocity, compression, cover hardness and COR, theresults of such tests are set forth in Table III below.

The balls were also tested for spin rate using a True Temper TestMachine configured to strike the balls with a driver and an 8-Iron. Alsotested for comparison purposes were conventional two piece “distance”balls (Titleist® HP2 Distance and Pinnacle® Gold). The test data for allof these balls is set forth in Tables 6-8 below.

TABLE 6 Compres- Cover COR³ Velocity¹ sion¹ Weight¹ Hardness² (at Ball(ft/s) (Ball) (oz) (Shore D) 125 ft/s) Pinnacle ® 252.5 95 1.605 680.809 Gold⁴ Titleist ® 253.0 99 1.600 71 0.810 HP2 Distance⁴ Ball 1251.9 81 1.610 71 0.814 Ball 2 252.3 84 1.584 72 0.814 Ball 3 252.2 841.588 71 0.813 Ball 4 251.9 84 1.590 69 0.810 ¹Average based on resultsfor 12 balls ²Average based on results for 3 balls ³Average based onresults for 6 balls ⁴Historical data for commercial balls

TABLE 7 Spin Rates For Driver Ball Type Launch Angle (°) Spin (rpm) ClubSpeed (ft/s) Pinnacle ® Gold 9.1 ± 0.3 3032 ± 135 158.6 ± 0.6 Titleist ®9.0 ± 0.3 2977 ± 60 158.6 ± 1.0 HP2 Distance Ball 1 9.1 ± 0.5 2973 ± 195158.4 ± 0.6 Ball 2 9.1 ± 0.5 3001 ± 66 158.9 ± 0.7 Ball 3 9.1 ± 0.4 3006± 121 158.9 ± 0.8

TABLE 8 Spin Rate For 8-Iron Ball Type Launch Angle (°) Spin (rpm) ClubSpeed (ft/s) Pinnacle ® Gold 19.2 ± 0.4 8160 ± 218 116.4 ± 0.1Titleist ® 19.4 ± 0.5 8375 ± 171 116.3 ± 1.3 HP2 Distance Ball 1 19.2 ±0.5 7970 ± 246 116.2 ± 0.7 Ball 3 19.3 ± 0.2 7972 ± 168 116.5 ± 0.9 Ball4 19.4 ± 0.3 7940 ± 171 117.0 ± 1.3

As shown by results reported in Tables 6-8, golf balls having anintermediate layer including NUCREL® 960, HYTREL® 3078, and ZnO have ahigh initial velocity and low spin rate. Moreover, the balls of thepresent invention have initial velocities approaching those ofconventional two-piece “distance” balls, but have a considerably lowercompression, which provides a much softer feel, more like a wound ball.Still further, these balls are easy to manufacture compared to theconventional wound ball. Thus, these balls provide the advantages of twopiece “distance” balls with low spin rates and high velocity, but alsoprovide a softer feel than such balls.

Example 5

Multilayer golf balls were made having intermediate layers formed from ablend including 20 percent NUCREL® 960, 57 percent HYTREL® 3078, and 23percent ZnO. This intermediate layer blend was injection molded aboutcores formed from the batch formulation set forth in Table 5. A coverwas formed by injection molding a blend of 50 percent SURLYN® 7940, 47percent SURLYN® 8940, and 3 percent SURLYN® 8660 around the intermediatelayer and subsequently finishing the balls using conventional clearcoating and buffing techniques.

The balls were tested for initial velocity, compression, cover hardnessand COR, as well as for spin rate when struck by a driver and an 8-Ironusing a True Temper Test Machine. The results of such tests are setforth below in Tables 9-11 below.

TABLE 9 Cover Velocity¹ Compression¹ Weight¹ Hardness² COR³ Specific(ft/s) (Ball) (oz) (Shore D) (at 125 ft/s) Gravity 251.5 82 1.607 690.801 1.27 ¹Average based on results for 12 balls ²Average based onresults for 3 balls ³Average based on results for 6 balls

TABLE 10 Club Launch Angle (°) Spin (rpm) Club Speed (ft/s) Driver  9.2± 0.5 3015 ± 221 160.3 ± 0.7 8 Iron 19.3 ± 0.6 7807 ± 252 115.6 ± 0.8

TABLE 11 Mantle Layer Compositions and Properties Flex Tensile HardnessResilience Modulus Modulus % Strain Sample (Shore D) (%) (psi) (psi) atBreak 1A 0% Estane 58091 28 54 1,720 756 563 100% Estane 58861 1B 25%Estane 58091 34 41 2,610 2,438 626 75% Estane 58861 1C 50% Estane 5809144 31 10,360 10,824 339 50% Estane 58861 1D 75% Estane 58091 61 3443,030 69,918 149 25% Estane 58861 1E 100% Estane 58091 78 46 147,240211,288 10 0% Estane 58861 2A 0% Hytrel 5556 40 47 8,500 7,071 527 100%Hytrel 4078 2B 25% Hytrel 5556 43 51 10,020 9,726 441 75% Hytrel 4078 2C50% Hytrel 5556 45 47 12,280 10,741 399 50% Hytrel 4078 2D 75% Hytrel5556 48 53 13,680 13,164 374 25% Hytrel 4078 2E 100% Hytrel 5556 48 5212,110 15,231 347 0% Hytrel 4078 3A 0% Hytrel 5556 30 62 3,240 2,078 810100% Hytrel 3078 No Break 3B 25% Hytrel 5556 37 59 8,170 5,122 685 75%Hytrel 3078 3C 50% Hytrel 5556 44 55 15,320 10,879 590 50% Hytrel 30783D 75% Hytrel 5556 53 50 19,870 16,612 580 25% Hytrel 3078 3E 100%Hytrel 5556 58 50 24,840 17,531 575 0% Hytrel 3078 4A 0% Hytrel 4078 4651 11,150 8,061 597 100% Pebax 4033 4B 25% Hytrel 4078 46 53 10,6307,769 644 75% Pebax 4033 4C 50% Hytrel 4078 45 52 9,780 8,117 564 50%Pebax 4033 4D 75% Hytrel 4078 42 53 9,310 7,996 660 25% Pebax 4033 4E100% Hytrel 4078 40 51 9,250 6,383 531 0% Pebax 4033 5A 0% Hytrel 307877 50 156,070 182,869 9 100% Estane 58091 5B 25% Hytrel 3078 65 4887,680 96,543 33 75% Estane 58091 5C 50% Hytrel 3078 52 49 53,940 48,941102 50% Estane 58091 5D 75% Hytrel 3078 35 54 12,040 6,071 852 25%Estane 58091 5E 100% Hytrel 3078 29 50 3,240 2,078 810 0% Estane 58091No Break 6A 100% Kraton 1921 29 59 24,300 29,331 515 0% Estane 58091 0%Surlyn 7940 6B 50% Kraton 1921 57 49 56,580 — 145 50% Estane 58091 0%Surlyn 7940 6C 50% Kraton 1921 56 55 28,290 28,760 295 0% Estane 5809150% Surlyn 7940 7A 33.3% Pebax 4033 48 50 41,240 30,032 294 33.3% Estane58091 33.3% Hytrel 3078 7B 30% Pebax 4033 48 50 30,650 14,220 566 40%Estane 58091 10% Hytrel 3078 7C 20% Pebax 4033 41 54 24,020 16,630 51240% Estane 58091 40% Hytrel 3078

While it is apparent that the illustrative embodiments of the inventionherein disclosed fulfill the objectives stated above, it will beappreciated that numerous modifications and other embodiments may bedevised by those skilled in the art. For instance, the thermoformingprocesses described herein may be used to form any portion of the ball.Likewise, the thermoformed shells may be placed around golf ball coresand any other golf ball component. Therefore, it will be understood thatthe appended claims are intended to cover all such modifications andembodiments which come within the spirit and scope of the presentinvention.

1. A method of making a golf ball comprising the steps of: forming acore having a core hardness; providing a roll stock comprising a firstlayer having a first hardness, a second layer having a second hardness,and a third layer having a third hardness, wherein at least one of thefirst, second, and third layers is formed of a thermoset material,wherein the thermoset material comprises a thermoset polybutadienematerial and wherein at least one of the first, second, and third layersis formed from a thermoplastic material, and wherein the first, second,and third hardnesses differ by about 3 Shore D to about 20 Shore D, andwherein the first hardness is greater than the core hardness; heatingthe roll stock to a softening point; forcing the roll stock against aplurality of molds; cooling the plurality of molds; removing the rollstock from the plurality of molds to form a plurality of shells;positioning two of the plurality of shells to surround the core; andforming a cover from a castable reactive liquid material.
 2. The methodaccording to claim 1, wherein the step of forcing comprises forcing theroll stock against each of the plurality of molds by vacuum or pressure.3. The method of claim 1, wherein a mold cycle occurs from the step offorcing to the step of removing, and wherein the mold cycle is about 30seconds or less.
 4. The method of claim 1, wherein the formed cover hasa thickness of about 0.05 inches or less.
 5. The method of claim 1,wherein the golf ball has a compression of about 85 or less.
 6. Themethod of claim 1, wherein the step of forming a cover comprises castingthe cover around the golf ball.
 7. A method of making a golf ballcomprising the steps of: forming a core; providing a roll stockcomprising at least two layers wherein at least one of the two layers isformed of a thermoset material, wherein the thermoset material ispolybutadiene; wherein the roll stock further comprises at least onesheet of material formed from a thermoplastic material; heating the rollstock to a softening point; engaging in a mold cycle comprising thesteps of: forcing the roll stock against a plurality of molds; coolingthe plurality of molds; removing the roll stock from the plurality ofmolds to form a plurality of shells, wherein the mold cycle is about 30seconds or less; positioning two of the plurality of shells to surroundthe core; and forming a cover disposed about the shells comprising acastable reactive liquid material having a hardness of less than 60Shore D.
 8. The method of claim 7, wherein the cover comprises an innerlayer and an outer layer.
 9. The method of claim 8, wherein the outerlayer is cast.
 10. The method of claim 7, wherein the cover has athickness of 0.05 inches or less.
 11. The method of claim 8, wherein theinner layer comprises an ionomer resin.